Medical lead for treating obstructive sleep apnea (OSA) with electrical stimulation

ABSTRACT

A lead for delivering electrical stimulation therapy is described. The lead includes an elongated member defining a longitudinal axis, one or more electrodes disposed at a distal end of the elongated member, a plurality of collars located along the longitudinal axis, and one or more fixation members. At least one of the fixation members is a bow-like member having a first connection point to a first collar of the plurality of collars and a second connection point to a second collar of the plurality of collars. The distal end of the elongated member is configured for insertion in a tongue of a patient such that the one or more electrodes are implanted proximate to one or more motor points of a protrusor muscle within the tongue of the patient and the bow-like member of the one or more fixation members is implanted within tissue of the tongue.

TECHNICAL FIELD

This disclosure relates to medical device systems and, moreparticularly, to medical device systems for delivery of electricalstimulation therapy.

BACKGROUND

Obstructive sleep apnea (OSA), which encompasses apnea and hypopnea, isa disorder in which breathing may be irregularly and repeatedly stoppedand started during sleep, resulting in disrupted sleep and reduced bloodoxygen levels. Muscles in a patient's throat intermittently relaxthereby allowing soft tissues of the throat to obstruct the upper airwaywhile sleeping and cause OSA. In patients with a smaller than normalairway, airflow into the upper airway can be obstructed by the tongue orsoft pallet moving to the back of the throat and covering the airway.Loss of air flow also causes unusual inter-thoracic pressure as a persontries to breathe with a blocked airway. Lack of adequate levels ofoxygen during sleep can contribute to abnormal heart rhythms, heartattack, heart failure, high blood pressure, stroke, memory problems, andincreased accidents during the day due to inadequate sleep.Additionally, loss of sleep occurs when a person is awakened during anapneic episode.

SUMMARY

The devices, systems, and techniques of this disclosure generally relateto an implantable medical device (IMD) system and methods for therapyfor obstructive sleep apnea (OSA) but can be extended to address otherpatient symptoms and disorders. With OSA, a patient's tongue may relaxduring sleep and block the patient's airway. Some example techniques toaddress OSA include electrically stimulating one or both hypoglossalnerves and/or motor points in the tongue of the patient. In response tothe electrical stimulation, the hypoglossal nerve(s) causes protrusormuscles (e.g., genioglossus and geniohyoid muscles) to contract and movethe tongue forward, thereby opening the airway. In some examples, inresponse to stimulating at the motor points of the protrusor muscles(e.g., a location where an axon of the hypoglossal nerve terminates at amuscle fiber), the protrusor muscles may contract to move the tongueforward, thereby opening the airway.

To stimulate the hypoglossal nerve(s) and/or motor points, a medicaldevice outputs electrical stimulation therapy via one or more electrodeson one or more implanted leads to cause the tongue to move forward. Amedical professional can implant the one or more leads into the tongueof the patient. The one or more implanted leads each include one or moreelectrodes coupled to the medical device (e.g., an implantable orexternal medical device that delivers electrical stimulation via one ormore electrodes on the lead).

With lead placement in the tongue, there may be issues related to howand where to place a lead to provide effective therapy. This disclosuredescribes example techniques for lead structures and/or lead placementthat may overcome one or more issues. Although the example techniquesare described with respect to lead placement in the tongue for treatingOSA, the example techniques should not be considered to be limited tolead placement in the tongue or limited to treating OSA.

As described in more detail, this disclosure describes exampletechniques to ensure that the lead remains in place after implantation.For example, the leads include one or more fixation members that aredeployed to affix the lead in place. In one or more examples, thefixation members, when deployed, includes a bow-like member that extendsoutward to define a peak.

In one example, the disclosure describes a lead for deliveringelectrical stimulation therapy, the lead comprising an elongated memberdefining a longitudinal axis and comprising a proximal end and a distalend, one or more electrodes disposed at the distal end of the elongatedmember, a plurality of collars located along the longitudinal axis ofthe elongated member, and one or more fixation members, wherein at leastone of the fixation members is a bow-like member having a firstconnection point to a first collar of the plurality of collars and asecond connection point to a second collar of the plurality of collars,wherein the distal end of the elongated member is configured forinsertion in a tongue of a patient such that the one or more electrodesare implanted proximate to one or more motor points of a protrusormuscle within the tongue of the patient and the bow-like member of theone or more fixation members is implanted within tissue of the tongue,and wherein the bow-like member, when deployed, defines a peak betweenthe first connection point and the second connection point of thebow-like member, and wherein the peak is a point of the bow-like memberthat is furthest from the elongated member.

In one example, the disclosure describes a system for deliveringelectrical stimulation therapy, the system comprising a lead fordelivering electrical stimulation therapy, the lead comprising anelongated member defining a longitudinal axis and comprising a proximalend and a distal end, one or more electrodes disposed at the distal endof the elongated member, a plurality of collars located along thelongitudinal axis of the elongated member, and one or more fixationmembers, wherein at least one of the fixation member is a bow-likemember having a first connection point to a first collar of theplurality of collars and a second connection point to a second collar ofthe plurality of collars, wherein the distal end of the elongated memberis configured for insertion in a tongue of a patient such that the oneor more electrodes are implanted proximate to one or more motor pointsof least one of a genioglossal or geniohyoid muscle within the tongue ofthe patient and the bow-like member of the one or more fixation membersis implanted within tissue of the tongue, and wherein the bow-likemember, when deployed, defines a peak between the first connection pointand the second connection point of the bow-like member, and wherein thepeak is a point of the bow-like member that is furthest from theelongated member, and a medical device comprising a connector assemblyconfigured to couple to the proximal end of the elongated member of thelead, wherein the medical device is configured to deliver electricalstimulation therapy via the one or more electrodes that cause at leastone of the genioglossal or geniohyoid muscle to protrude the tongue ofthe patient.

In one example, the disclosure describes a lead for deliveringelectrical stimulation therapy, the lead comprising an elongated memberdefining a longitudinal axis and comprising a proximal end and a distalend, wherein the elongated member has a diameter less than 1.5millimeter (mm), one or more electrodes disposed at the distal end ofthe elongated member, a plurality of collars located along thelongitudinal axis of the elongated member, and one or more fixationmembers, wherein at least one of the fixation members is a bow-likemember having a first connection point to a first collar of theplurality of collars and a second connection point to a second collar ofthe plurality of collars, and wherein the one or more fixation members,when deployed, comprise a triangular shape or a lobe shape, wherein thedistal end of the elongated member is configured for insertion in atongue of a patient such that the one or more electrodes are implantedproximate to one or more motor points of a protrusor muscle within thetongue of the patient and the bow-like member of the one or morefixation members is implanted within tissue of the tongue, and whereinthe bow-like member, when deployed, defines a peak between the firstconnection point and the second connection point of the bow-like member,and wherein the peak is a point of the bow-like member that is furthestfrom the elongated member, wherein a distance between the lead and thepeak of the bow-like member is approximately 2 millimeter, and wherein adistance between the distal end of the elongated member and the bow-likemember is less than or equal to 10 mm.

In one example, the disclosure describes a method of implanting a lead,the method comprising inserting a needle through tissue near a chin of apatient and through a tongue of the patient, inserting an introducerthrough an opening created by the needle, and inserting a lead throughthe introducer, the lead comprising an elongated member and one or moreelectrodes at a distal end of the elongated member such that the one ormore electrodes are implanted proximate to one or more motor points of aprotrusor muscle within the tongue of the patient, wherein inserting thelead comprises inserting the lead to have a shape of one of a helix, acompound helix, a wave shape, or saw-tooth shape, or having a loop inthe lead.

The details of one or more aspects of the disclosure are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the techniques described in this disclosurewill be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram of an implantable medical device (IMD)system for delivering obstructive sleep apnea (OSA) therapy.

FIG. 2 is a conceptual diagram of a lead used for OSA therapy accordingto one or more examples of this disclosure.

FIG. 3 is a conceptual diagram illustrating example locations of motorpoints where stimulation for OSA therapy may be delivered.

FIG. 4 is a block diagram illustrating example configurations ofimplantable medical devices (IMDs) which may be utilized in the systemof FIG. 1.

FIG. 5 is a block diagram illustrating an example configuration of anexternal programmer.

FIGS. 6A-6D are conceptual diagrams illustrating deployment of fixationmembers.

FIGS. 7A-7C are conceptual diagrams illustrating examples of deployedbow-like members.

FIG. 8 is a top perspective of a lead with deployed fixation members.

FIGS. 9A-9C are conceptual diagrams illustrating lead position afterimplantation.

FIG. 10 is a flowchart illustrating an example of lead implantation.

DETAILED DESCRIPTION

Medical devices, systems, and techniques for delivering electricalstimulation to the protrusor muscles of the tongue for the treatment ofobstructive sleep apnea (OSA) are described in this disclosure.Electrical stimulation is delivered to cause the tongue of a patient toenter a protruded state, during sleep, to avoid or reduce upper airwayobstruction. As used herein, the term, “protruded state” with regard tothe tongue refers to a position that is moved forward and/or downwardcompared to a non-stimulated position or a relaxed position of thetongue. The protruded state is a state associated with contraction(e.g., via innervation from nerves in response to electricalstimulation) of protrusor muscles of the tongue (also sometimes referredto as “protruder” muscles of the tongue) including the genioglossus andgeniohyoid muscles. A protruded state may be the opposite of a retractedand/or elevated position associated with the contraction of theretractor muscles (e.g., styloglossus and hyoglossus muscles) whichretract and elevate the tongue. Electrical stimulation is delivered tocause the tongue to move (e.g., by depolarizing the nerve(s) thatinnervate the genioglossus and/or geniohyoid muscles) to and maintain aprotruded state. As discussed above, the protruded state may preventcollapse or blockage of, open, or widen the upper airway of a patient toat least partially maintain or increase airflow (e.g., promoteunrestricted airflow or at least reduced restriction of airflow duringbreathing).

A surgeon implants one or more leads that each include one or electrodesinto the tongue such that the electrodes are proximate to a hypoglossalnerve and/or motor points (e.g., one or more locations where axons ofthe hypoglossal nerve terminate at respective muscle fibers of theprotrusor muscles). For example, there are two hypoglossal nerves in thetongue of the patient. In one example, one lead may be used to stimulate(e.g., by delivering electrical stimulation through one or moreelectrodes of the lead) one of the two hypoglossal nerves, one lead maybe used to stimulate both hypoglossal nerves, or two leads may be used,where each lead stimulates a respective one of the hypoglossal nerves.Stimulation of either or both hypoglossal nerves of the tongue can causecontraction of the protrusor muscles to reduce the effect of, orprevent, OSA.

There are multiple sets of motor points for each of the protrusormuscles on the left side and the right side. Each motor point mayinnervate one or more muscle fibers of the protrusor muscle. In oneexample, one lead may be used to stimulate motor points for theprotrusor muscles on one side of the tongue, one lead may be used tostimulate motor points for protrusor muscles on both sides of thetongue, or two leads may be used, where each lead stimulates arespective set of motor points for the protrusor muscles on each side.Stimulation of either or both sets of motor points of the tongue cancause contraction of the protrusor muscles to reduce the effect of, orprevent, OSA.

This disclosure describes examples of techniques related to implantationof the one or more leads in the tongue for treatment of OSA. Althoughthe example techniques are described with respect to OSA, the exampletechniques should not be construed as limited to OSA. Rather, theexample techniques described in this disclosure may be applicable tolead implantation for treatment of various conditions including leadimplantation for treatment of conditions where the lead is implanted ina location other than the tongue.

For treating OSA, once a location for implantation of a lead isselected, it may be desirable for the lead to remain implanted for manyyears. However, due to movement of the tongue, it may be possible forthe lead to migrate forward (e.g., closer to the tip of tongue andtoward the outward opening of the mouth), backward (e.g., away from thetip of tongue), or laterally (e.g., to the left or right in the tongue).This disclosure describes examples of fixation members that may be usedto fix (e.g., anchor) the lead within the tongue and minimize or reducethe movement of the lead once implanted. As described in more detail,because the lead may be implanted in tissue of the tongue, such asmuscle, the tongue may heal from the operation necessary forimplantation. In particular, following lead implantation, the tongue mayform scar tissue around the lead and the fixation member. The examplefixation members described in this disclosure may leverage the naturalscarring of the tissue around the fixation members to limit the movementof the lead.

In some cases, although the lead should remain implanted for many years,there may be times when it is desirable to reposition the lead or removethe lead. For example, after a trialing period is complete, due topatient discomfort, or due to other treatments for OSA, explantation ofa lead may be desirable. This disclosure describes examples where thefixation members can be retracted so that it is easier to reposition thelead or remove the lead with minimal impact to the tongue. As analternative, the fixation members may be configured to wholly orpartially dissolve following implantation, likewise facilitatingrepositioning or removal of the lead.

Moreover, in some examples, repetitive movement of the tongue can leadto breakage of the lead. This disclosure describes examples of leadplacement to allow for stress relief on the lead so that lead breakagedue to tongue movement is minimized or reduced.

FIG. 1 is a conceptual diagram of a medical system for delivering OSAtherapy. In system 10, implantable medical device (IMD) 16 and lead 20are implanted in patient 14. IMD 16 includes housing 15 enclosingcircuitry of IMD 16. In some examples, IMD 16 includes connectorassembly 17, which is hermetically sealed to housing 15 and includes oneor more connector bores for receiving a proximal end of at least onemedical electrical lead 20 used for delivering OSA therapy. Although onelead 20 is illustrated in FIG. 1, there may be one or more leads 20 towhich IMD 16 is coupled.

Lead 20 may include a flexible, elongate lead body 22, also calledelongated member 22, that extends from lead proximal end 24 to leaddistal end 26. As illustrated, lead 20 includes one or more electrodes30 that are carried along a lead distal portion adjacent lead distal end26 and are configured for insertion within the protrusor muscles 42A,42B, and 46 of tongue 40. As one example, the genioglossus muscleincludes oblique compartment 42A and horizontal compartment 42B. In thisdisclosure, the genioglossus muscle is referred to as protrusor muscle42. Protrusor muscle 46 is an example of the geniohyoid muscle.

As illustrated, distal end 26 of lead 20 includes one or more electrodes30. Proximal end 24 of lead 20 includes one or more electrical contactsto connect to connector assembly 17. Lead 20 also includes conductorssuch as coils or wires that connect respective electrodes 30 torespective electrical contacts at proximal end 24 of lead 20.

While protrusor muscles 42 and 46 are described, the example techniquesdescribed in this disclosure are not limited to stimulating protrusormuscles 42 and 46. Also, FIG. 1 illustrates one set of protrusor muscles42 and 46 (e.g., on a first side of tongue 40). The other side of tongue40 also includes protrusor muscles. For instance, a left side of tongue40 includes a first set of protrusor muscles 42 and 46, and a right sideof tongue 40 includes a second set of protrusor muscles.

In some examples, a surgeon may implant one or more leads 20 such thatone or more electrodes 30 are implanted within soft tissue, such asmusculature, proximate to medial branches of one or both hypoglossalnerves. In some examples, one or more electrodes 30 may be approximately5 mm (e.g., 2 mm to 8 mm) from a major trunk of the hypoglossal nerve.In some examples, one or more electrodes 30 may be placed in an area ofprotrusor muscles 42 and 46 that include motor points, where each nerveaxon terminates in the muscle (also called the neuro-muscular junction).The motor points are not at one location but spread out in the protursormuscles. Leads 20 may be implanted such that one or more electrodes 30may be generally in the area of the motor points (e.g., such that themotor points are within 1 to 10 mm from one or more electrodes 30).Examples of motor points for protrusor muscles 42 and 46 are illustratedin more detail with respect to FIG. 3.

Tongue 40 includes a distal end (e.g., tip of tongue 40), and electrodes30 may be implanted proximate to root 49 of tongue 40. The surgeon mayimplant one or more leads 20 such that one or more electrodes areimplanted proximate to root 49 of tongue 40, as illustrated in FIG. 1.For example, the location for stimulation for the genioglossus muscle 42may be approximately 30 mm (e.g., 25 mm to 35 mm) from the Symphsis ofthe jaw (e.g., where the genioglossus and hypoglossal muscles insert).The location for stimulation for the geniohyoid muscle 46 may beapproximately 40 mm (e.g., 35 mm to 45 mm) from the Symphsis. For boththe genioglossus muscle 42 and the geniohyoid muscle 44, the locationfor stimulation may be approximately 11 mm (e.g., 7 mm to 15 mm) lateralto the midline on both the right and left sides of tongue 40 forstimulating respective hypoglossal nerves. In some examples, rather thanstimulating hypoglossal nerves, the examples described in thisdisclosure may be configured for stimulating the motor points, asdescribed in more detail with respect to FIG. 3. Stimulating the motorpoints may result in indirect activation of the hypoglossal nerve, butmay generally be stimulating at a different location than directstimulation to the hypoglossal nerve. As a result, in some examples,simulation of one or more motor points may result in more preciseactivation of muscle fibers than may be possible with stimulation of thehypoglossal nerve itself.

One or more electrodes 30 of lead 20 may be ring electrodes, segmentedelectrodes, partial ring electrodes or any suitable electrodeconfiguration. Ring electrodes extend 360 degrees around thecircumference of the lead body of lead 20. Segmented and partial ringelectrodes each extend along an arc less than 360 degrees (e.g., 90-120degrees) around the outer circumference of the lead body of lead 20. Inthis manner, multiple segmented electrodes may be disposed around theperimeter of lead 20 at the same axial position of the lead. In someexamples, segmented electrodes may be useful for targeting differentfibers of the same or different nerves at respective circumferentialpositions with respect to the lead to generate different physiologicaleffects (e.g., therapeutic effects), permitting stimulation to beoriented directionally. In some examples, lead 20 may be, at least inpart, paddle-shaped (e.g., a “paddle” lead), and may include an array ofelectrodes arranged as contacts or pads on a common surface, which mayor may not be substantially flat and planar.

As described above, in some examples, electrodes 30 are withinmusculature of tongue 40. Accordingly, one or more electrodes 30 may be“intramuscular electrodes.” Intramuscular electrodes may be differentthan other electrodes that are placed on or along a nerve trunk orbranch, such as a cuff electrode, used to directly stimulate the nervetrunk or branch. The example techniques described in this disclosure arenot limited to intramuscular electrodes and may be extendable toelectrodes placed closer to a nerve trunk or branch of the hypoglossalnerve(s). Also, in some examples, rather than one or more electrodes 30being “intramuscular electrodes,” one or more electrodes 30 may beimplanted in connective tissue or other soft tissue proximate to thehypoglossal nerve.

In some examples, lead 20 may be configured for advancement through thesoft tissue, which may include the protrusor muscle tissue, to anchorelectrodes 30 in proximity to the hypoglossal nerve(s) that innervateprotrusor muscles 42 and/or 46 and/or motor points that connect axons ofhypoglossal nerve(s) to respective muscle fibers of protrusor muscles 42and/or 46. However, in some examples, lead 20 may be configured foradvancement through vasculature of tongue 40. As one example, a surgeonmay implant lead 20 in the lingual veins near the hypoglossal nervethough venous access in the subclavian vein. In such examples, one ormore electrodes 30 may be “intravascular electrodes.”

As described above, electrical stimulation therapy generated by IMD 16and delivered via one or more electrodes 30 may activate protrusormuscles 42 and 46 to move tongue 40 forward, for instance, to promote areduction in obstruction or narrowing of the upper airway 48 duringsleep. As used herein, the term “activated” with regard to theelectrical stimulation of protrusor muscles 42 and 46 refers toelectrical stimulation that causes depolarization or an action potentialof the cells of the nerve (e.g., hypoglossal nerve(s)) or stimulation atthe neuro-muscular junction between the nerve and the protrusor muscles(e.g., at the motor points) innervating protrusor muscles 42 and 46 andmotor points and subsequent depolarization and mechanical contraction ofthe protrusor muscle cells of protrusor muscles 42 and 46. In someexamples, protrusor muscles 42 and 46 may be activated directly by theelectrical stimulation therapy.

Protrusor muscles 42 and/or 46, on a first side of tongue 40 (e.g., theleft or right side of tongue 40), may be activated by a medial branch ofa first hypoglossal nerve, and the protrusor muscles, on a second sideof tongue 40 (e.g., the other of the left or right side of tongue 40),may be activated by a medial branch of a second hypoglossal nerve. Themedial branch of a hypoglossal nerve may also be referred to as theXIIth cranial nerve. The hyoglossus and styloglossus muscles (not shownin FIG. 1), which cause retraction and elevation of tongue 40, areactivated by a lateral branch of the hypoglossal nerve.

One or more electrodes 30 may be used to deliver bilateral or unilateralstimulation to protrusor muscles 42 and 46 via the medial branch of thehypoglossal nerve or branches of the hypoglossal nerve (e.g. such as atthe motor point where a terminal branch of the hypoglossal nerveinterfaces with respective muscle fibers of protrusor muscles 42 and/or46). For example, one or more electrodes 30 may be coupled to outputcircuitry of IMD 16 to enable delivery of electrical stimulation pulsesin a manner that selectively activates the right and left protrusormuscles (e g , in a periodic, cyclical or alternating pattern) to avoidmuscle fatigue while maintaining upper airway patency. Additionally, oralternatively, IMD 16 may deliver electrical stimulation to selectivelyactivate protrusor muscles 42 and/or 46 or portions of protrusor muscles42 and/or 46 during unilateral stimulation of the left or rightprotrusor muscles.

In some examples, one lead 20 may be implanted such that one or more ofelectrodes 30 deliver electrical stimulation to stimulate the lefthypoglossal nerve or motor points of protrusor muscles on the left sideof tongue, and therefore cause the left protrusor muscles to activate.In such examples, the electrical stimulation from one or more electrodes30 may not be of sufficient amplitude to stimulate the right hypoglossalnerve or motor points of protrusor muscles on the right side of tongueand cause the right protrusor muscles to activate. In some examples, onelead 20 may be implanted such that one or more of electrodes 30 deliverelectrical stimulation to stimulate the right hypoglossal nerve or motorpoints of protrusor muscles on the right side of tongue, and thereforecause the right protrusor muscles to activate. In such examples, theelectrical stimulation from one or more electrodes 30 may not be ofsufficient amplitude to stimulate the left hypoglossal nerve or motorpoints of protrusor muscles on the left side of tongue and cause theleft protrusor muscles to activate. Accordingly, in some examples, twoleads like lead 20 may be implanted to stimulate each of the left andright hypoglossal nerves and/or motor points of respective protrusormuscles on the left and right side of tongue 40.

In some examples, one lead 20 may be implanted substantially in themiddle (e.g., center) of tongue 40. In such examples, one or moreelectrodes 30 may deliver electrical stimulation to both hypoglossalnerves or motor points of both muscles on the both sides of tongue 40,causing both hypoglossal nerves or motor points to activate respectiveleft and right protrusor muscles. It may be possible to utilize currentsteering and field shaping techniques such that one or more electrodes30 deliver first electrical stimulation that stimulates the lefthypoglossal nerve or motor points of protrusor muscles on the left sideof tongue 40 with little to no stimulation of the right hypoglossalnerve or motor points of protrusor muscles on the right side of tongue40, and then one or more electrodes 30 deliver second electricalstimulation that stimulates the right hypoglossal nerve or motor pointsof protrusor muscles on the right side of tongue with little to nostimulation of the left hypoglossal nerve or motor points of protrusormuscles on the left side of tongue. In examples where two leads likelead 20 are utilized, each lead may alternate delivery of stimulation torespective hypoglossal nerves or motor points. In this way, IMD 16 maystimulate one hypoglossal nerve or one set of motor points and then theother hypoglossal nerve or another set of motor points, which can reducemuscle fatigue.

For instance, continuous stimulation may cause protrusor muscles to becontinuously in a protruded state. This continuous contraction may causeprotrusor muscles 42 and/or 46 to fatigue. In such cases, due tofatigue, the stimulation may not cause protrusor muscles 42 and/or 46 tomaintain a protruded state (or higher intensity of the electricalstimulation may be needed to cause protrusor muscles 42 and/or 46 toremain in the protruded state). By stimulating one set of protrusormuscles (e.g., left or right), a second set (e.g., other of left orright) of protrusor muscles can be at rest. Stimulation may thenalternate to stimulate the protrusor muscles that were at rest andthereby maintain protrusion of tongue 40, while permitting the protrusormuscles 42 and/or 46 that were previously activated to rest. Hence, bycycling between alternate stimulation of the left and right protrusormuscles, tongue 40 can remain in the protruded state, while one of thefirst or second set of protrusor muscles is at rest.

In some examples, one lead 20 may be implanted laterally or diagonallyacross tongue 40 such that some of electrodes 30 on lead 20 can be usedto stimulate the left hypoglossal nerve and/or motor points of theprotrusor muscles on the left side of tongue 40 and some of electrodes30 on the same lead 20 can be used to stimulate the right hypoglossalnerve and/or motor points of the protrusor muscles on the right side oftongue 40. In such examples, IMD 16 may selectively deliver electricalstimulation to a first hypoglossal nerve and/or first motor points ofthe protrusor muscles on the a first side of tongue 40 via a first setof one or more electrodes 30, and then deliver electrical stimulation toa second hypoglossal nerve and/or /or second set of motor points of theprotrusor muscles on a second side of tongue 40 via a second set of oneor more electrodes 30. This may be another way in which to reduce musclefatigue.

Lead proximal end 24 includes a connector (not shown in FIG. 1) that maybe coupled to connector assembly 17 of IMD 16 to provide electricalconnection between circuitry enclosed by the housing 15 of IMD 16. Leadbody 22 encloses electrical conductors extending from each of one ormore electrodes 30 to the proximal connector at proximal end 24 toprovide electrical connection between output circuitry of IMD 16 and theelectrodes 30.

There may be various ways in which lead 20 is implanted in patient 14.As one example, a surgeon may insert a needle (also called introducerneedle) through the lower part of the jaw and in tongue 40 starting fromthe back of tongue 40. The surgeon may insert the needle until a distaltip of the needle reaches a point at or adjacent to the tip of tongue40, angling the needle to be extend proximate to the hypoglossal nerve(e.g., left or right hypoglossal nerve) and to the motor points. In someexamples, the needle may include one or more electrodes (e.g., one tofour electrodes) at the distal end, and the surgeon may cause the one ormore electrodes of the needle to output electrical stimulation (e.g., inthe form of controlled current pulses or controlled voltage pulses),which in turn causes a physiological response such as activation ofprotrusor muscles 42 and/or 46 and protrusion of tongue 40. The surgeonmay adjust the location of the needle based on the physiologicalresponse to determine a location in tongue 40 that provides effectivetreatment. Using a needle with stimulating electrodes is not necessaryin every example.

Once the needle is in place, the surgeon may insert a guidewire (orsimply “guide”) through the needle and anchor the guidewire (e.g., withtines on the guidewire) to tissue of tongue 40. Then, the surgeon mayremove the needle, leaving behind the guidewire.

The surgeon may place an introducer, which may or may not include adilator, over the guidewire through the opening created by the needle.The introducer may be referred to as an introducer, introducer sheath,or introducer/dilator. In some examples, the introducer may optionallyinclude one or more electrodes that the surgeon can use to teststimulation of tongue 40 to ensure that lead 20 will be located in thecorrect location, relative to the target nerve tissue (e.g., motorpoints). Once the introducer is in place, the surgeon may remove theguidewire. In some examples, the introducer may be flexible or curved toease placement of the introducer in patient 14.

The surgeon may prepare lead 20 for insertion. In some examples, theremay be an additional sheath placed over lead 20 that holds fixationmember(s), such as those described with respect to FIG. 2, in place. Useof such an additional sheath is not necessary in all examples. Becauselead 20 may be highly flexible, in some examples, the surgeon may placea stylet through lead 20 to provide some rigidity and allow lead 20 totraverse through tongue 40 under a pushing force. Use of a stylet maynot be necessary in all examples.

The surgeon may put lead 20 through the introducer such that one or moreelectrodes 30 are proximate to the hypoglossal nerve (e.g., such thatdistal end 26 is near tip of tongue as one non-limiting example).Electrodes 30 may be proximate to the hypoglossal nerve and/or motorpoints of the protrusor muscles due to the needle creating an openingnear the hypoglossal nerve and/or motor points of the protrusor muscle.The surgeon may then tunnel proximal end 24 of lead 20 back to aconnection with IMD 16.

In this manner, the surgeon may implant one lead 20. In examples wheretwo or more leads are implanted, the surgeon may perform steps similarto those described above.

The above describes some example techniques for lead placement, and theexamples described in this disclosure should not be considered limitedto such examples of lead placement. Moreover, in some examples, thesurgeon may use imaging techniques, such as fluoroscopy, duringimplantation to verify proper placement of lead 20, the needle, and/orthe introducer.

FIG. 1 illustrates the location of IMD 16 as being within or proximateto the neck of patient 14. However, IMD 16 may be implanted in variousother locations. As one example, the surgeon may implant IMD 16 in theleft or right pectoral region. For instance, the surgeon may plan onimplanting IMD 16 in the left pectoral region unless another medicaldevice is already implanted in the left pectoral region. If anothermedical device is already implanted in the left pectoral region, thesurgeon may then implant IMD 16 in the right pectoral region. There mayother locations where the surgeon may implant IMD 16 such as the back ofpatient 14. The example techniques are not limited to any particularimplant location of IMD 16.

In accordance with one or more examples described in this disclosure,lead 20 may be configured for implantation in tongue 40 such thatpost-implantation there may be little to no lead migration of lead 20.In some examples, although leaving lead 20 in place for many years afterimplantation may be desirable, there may be instances where adjustmentor removal of lead 20 may be desired. This disclosure describes examplesof lead 20 configured for adjustment and removal in a way that reducestrauma to patient 14.

Moreover, tongue 40 may move much more during the life of patient 14 ascompared to other anatomy where a medical therapy lead may be implanted.Due to the relatively large number of times that tongue 40 moves, theremay be a higher probability that lead 20 breaks. In some examples, lead20 may be implanted in such a manner so as to reduce the chance of lead20 breaking.

As described above, lead 20 is implanted to stimulate the hypoglossalnerve or motor points of the protrusor muscles. There may be certainunique challenges associated with lead 20 stimulating the hypoglossalnerve or motor points of the protrusor muscles in tongue 40 as comparedto another lead being located in other portions of the body such as nearthe sacral nerve, spinal cord or brain or in a blood vessel. As oneexample, inside tongue 40, there is a chance for lead 20 to migrateproximally (e.g., towards the back of tongue 40) and distally (e.g.,towards the tip of tongue 40).

To reduce the migration of lead 20, lead 20 may include one or morefixation members. The fixation members may extend outward from lead 20and into the tissue of tongue 20. For example, FIG. 1 illustratesbow-like members 29A and 29B and one or more tines 31 located proximallyon lead 20. Bow-like members 29A and 29B and one or more tines 31 areexamples of the fixation members. FIG. 1 illustrates one set of bow-likemembers 29A and 29B configured as lobes and three tines 31. However, insome examples, there may be a plurality of bow-like members, likebow-like members 29A and 29B, and no tines. In some examples, there maybe only tines 31, arranged differently than in the example of FIG. 1 tominimize lead migration.

Lead 20 may include plurality of pairs, trios, or quads of bow-likemembers. For instance, FIG. 1 illustrates a pair of bow-like members 29Aand 29B that are axially at the same longitudinal location on lead 20.In some examples, there may be three bow-like members or four bow-likemembers located axially at the same longitudinal location on lead 20.

As described in more detail below, such as with respect to FIGS. 6A-6D,bow-like members 29A and 29B may each be fastened at opposite ends ofrespective collars located axially along elongated lead body 22. Each ofthe collars may be slidable along lead body 22 but one of the collarsmay be fixed in position. The sliding of the collars (e.g., sliding ofthe collars towards distal end 26) causes bow-like members 29A and 29Bto extend outward to achieve an arc-like, triangle-like, or lobe-likeprotrusion depending on how close the collars are pushed. In someexamples, the slidable collars may be limited so that bow-like members29A and 29B, when extended, form arc-like fixation members, or so thatbow-like members 29A and 29B can be extended further from formingarc-like fixation members but limited to forming triangle-like fixationmembers, or so that bow-like members 29A and 29B can be extended furtherfrom forming triangle-like fixation members but limited to forminglobe-like fixation members.

Once the fixation members are deployed with tissue of tongue 40, thefixation members may remain deployed due to the tissue. In someexamples, the slidable collars may be locked in place so that thecollars cannot slide back, unless or until the collars are intentionallyslid back to retract the bow-like members flat against lead body 22.

As illustrated in FIG. 1, at least one fixation member (e.g., bow-likemembers 29A and 29B) are implanted within the tissue of tongue 40.Having fixation members like bow-like members 29A and 29B may bebeneficial for reducing migration of lead 20. For example, afterimplantation and deployment of bow-like members 29A and 29B, tissue oftongue 40 may being to scar around lead 20 and/or bow-like members 29Aand 29B. The scarring of the tissue of tongue 40 around bow-like members29A and 29B may keep lead 20 in place. In other words, bow-like members29A and 29B provide anchoring of lead 20 within tongue 40 to hold thelead in place, promote further anchoring of the lead with formation ofscar tissue, and thereby reduce lead migration.

Although bow-like members 29A and 29B are illustrated as lobes, theexample techniques are not so limited. Lobes may be curved bow-likemembers that start and return back to lead body 22, where a distancebetween the start and return points on lead body 22 is relatively close.However, in some examples, one or more fixation members may betriangular (e.g., not curved) or other shapes. For instance, one or morefixation members, examples of which include bow-like members 29A and29B, extend outward to define a peak that is substantially perpendicularto the longitudinal axis of lead 20. As one example, the peak refers toan outermost location on the fixation member, relative to a longitudinalaxis of lead 20, having at least two connections back to lead 20, wherethe tangent line at the peak is parallel to lead 20.

For example, in examples where the fixation members are bow-like members29A and 29B, the peak may be the highest point on the curve of bow-likemembers 29A and 29B. In such examples, there is curve towards the peak,which forms one of the connections to lead 20, and a curve away from thepeak, which forms another of the connections to lead 20. In exampleswhere the fixation members are triangular, there may be two points onlead 20 that define a width of the triangle, and the third pointconnects to the two points and forms a peak.

Accordingly, lead 20 is an example of a lead for delivering electricalstimulation therapy. Lead 20 includes an elongated member (e.g., thelead body 22) defining a longitudinal axis (e.g., lengthwise axis oflead 20) that includes proximal end 24 and distal end 26. There are oneor more electrodes 30 disposed at distal end 26 of the elongated member.At distal end 26 should not be interpreted to mean that there is anelectrode exactly at distal end 26, although having an electrode exactlyat distal end is possible. Rather, “at the distal end” means that one ormore electrodes 30 are proximate to distal end 26 including possiblybeing exactly at distal end 26.

Lead 20, along the elongated member, also includes one or more fixationmembers like one or more bow-like members 29A and 29B and tines 31.However, the fixation members may only be a plurality of bow-likemembers, like bow-like members 29A and 29B, plurality of triangles, orsome combination, and no tines 31.

In some examples, the fixation members may be held against the elongatedmember (e.g., in a retracted position), until the fixation members aredeployed. After deployment, the fixation members extend into tissue andhold lead 20 in place (e.g., minimize lead migration). For instance, thefixation members hold lead 20 in place by bearing against tissue toprovide friction or interference fit initially, and the provide anenvironment for scar tissue to form for long-term fixation.

For instance, distal end 26 of the elongated member is configured forinsertion in tongue 40 of patient 14 such that one or more electrodes 30are implanted proximate to one or more motor points of a protrusormuscle (e.g., protrusor muscles 42 and/or 46) within tongue 40 and atleast one fixation member (e.g., one or both of bow-like members 29A and29B) of the one or more fixation members is implanted within tissue oftongue 40. The at least one fixation member, when deployed, includes abow-like member that defines a peak that is substantially perpendicularto the longitudinal axis of the elongated member of lead 20.“Substantially perpendicular” means that the peak is within a range of75° to 105°, and generally at 90° relative to the longitudinal axis ofthe elongated member (e.g., leady body) of lead 20.

For example, the bow-like member includes a two fastening points onrespective collars on lead body 22 (also called elongated member 22), asdescribed below with respect to FIGS. 6A-6D. A line extending from amiddle point that is in the middle of two fastening points on respectivecollars on lead body 22, that extends at substantially 90° (e.g., 75° to105°) relative to the lead body 22, intersects the peak defined by thebow-like member.

FIG. 2 is a conceptual diagram of lead 20 used for OSA therapy accordingto one or more examples. For instance, FIG. 2 illustrates distal portion28 of lead 20, where distal portion 28 of lead 20 may form part of lead20 that is implanted in tongue 40, as described above. Lead 20 mayinclude one or more electrodes 30, and FIG. 2 shows lead 20 with fourelectrodes 30A, 30B, 30C, and 30D (collectively referred to as“electrodes 30”) spaced apart longitudinally along lead body 22. Leadbody 22 is an example of the elongated member of lead 20. For instance,lead body 22 and the elongated member of lead 20 are the same.

Lead body 22 (e.g., elongated member of lead 20) may be a flexible leadbody through which insulated electrical conductors extend to respectiveelectrodes 30. The distal most electrode 30A may be adjacent orproximate to lead distal end 26. Each of electrodes 30 may be spacedproximally from the respective adjacent one of electrodes 30 byrespective interelectrode distances 34, 35 and 36.

The electrical conductors that extend to respective electrodes 30 fromproximal contacts at proximal end 24 may be arranged as a plurality ofcoils. The coils may increase the flexibility of lead 20 so that lead 20can bend at the distal end. In some examples, the coils may be exposedalong the locations of electrodes 30 such that the coils form electrodes30. Rather than electrodes 30 being pad electrodes or ring electrodes,the coils form electrodes 30 and, in this way, electrodes 30 arebendable, providing additional flexibility. In such examples, electrodes30 are coil electrodes.

In some examples, each one of electrodes 30 may have equivalentelectrode lengths 31 (e.g., longitudinal extend of electrodes 30 alonglead body 22). Lengths 31 may be approximately 3 mm, but less than 3 mmlengths are possible. However, electrodes 30 may have electrode lengths31 that are different from each other in order (e.g., to optimizeplacement of the electrodes 30 or the resulting electrical field ofstimulation relative to targeted stimulation sites corresponding to leftand right hypoglossal nerves or branches of hypoglossal nerves and/ormotor points of protrusor muscles 42 and/or 46).

Spacing 34, 35, and 36 are shown to be approximately equal in FIG. 2.However, in other examples, the interelectrode spacings 34, 35, and 36may be different from each other (e.g., in order to optimize placementof electrodes 30 relative to the targeted stimulation sites). Spacing34, 35, and 36 may be approximately 3 mm but less than 3 mm spacing ispossible. In some examples, for a bipolar configuration, electrodes 30Aand 30B form an anode and cathode pair for delivering bipolarstimulation in one portion of the protrusor muscles 42 and/or 46 (e.g.,either the left or right protrusor muscles or a proximal and/or distalportion of portion of the protrusor muscles). Electrodes 30C and 30D mayform a second anode and cathode pair for delivering bipolar stimulationin a different portion of protrusor muscles 42 and/or 46 (e.g., theother of the left or right portions or the other of the proximal ordistal portions). Accordingly, the interelectrode spacing 35 between thetwo bipolar pairs 30A, 30B and 30C, 30D may be different than theinterelectrode spacing 34 and 36 between the anode and cathode withineach bipolar pair 30A, 30B and 30C, 30D.

In some examples, for a unipolar configuration, housing 15 of IMD 16 mayinclude an electrode that functions as cathode, and part of the anodeand cathode pair with one of electrodes 30. In some examples, housing 15itself may function as the cathode of an anode, cathode pair, with oneof electrodes 30 forming the anode. Housing 15 may be anode in someexamples.

In one example, the total distance D1 encompassed by electrodes 30 alongthe distal portion 28 of lead body 22 may be between approximately 20and 30 millimeters. In one example, the total distance D1 is betweenapproximately 20 and 22 millimeters. However, as an alternative, thedistances may be shorter. As one example, the distance from distalportion 28 to one or more fixation members 32 may be approximately 10millimeters to ensure that at least one of the one or more fixationmembers 32 is implanted within tongue 40.

The interelectrode spacings 34 and 36 within a proximal electrode pair30C, 30D and a distal electrode pair 30A, 30B, respectively, may be in arange of approximately 2 to 5 millimeters in some examples. Theinterelectrode spacing 35 separating the distal and proximal pairs 30A,30B and 30C, 30D may be greater than the interelectrode spacings 34 and36. For example, the interelectrode spacing 35 may be in a range ofapproximately 4 to 6 millimeters in some examples. In one example, eachof electrodes 30 has an electrode length 31 of approximately 3 mm, andeach of interelectrode spacings 34, 35 and 36 is approximately 3 mm.

In FIG. 2, each of electrodes 30 is a circumferential ring electrodewhich may be uniform in diameter with lead body 22. As described above,electrodes 30 may include other types of electrodes such as a tipelectrode, a helical electrode, a coil electrode, as described above,segmented electrodes, a button electrode as examples. For instance, thedistal most electrode 30A may be provided as a tip electrode at the leaddistal end 26 with the remaining three electrodes 30B, 30C, and 30Dbeing ring electrodes. In some examples, when electrode 30A ispositioned at the distal end 26, electrode 30A may be a helicalelectrode configured to screw into the muscle tissue at the implant siteto additionally serve as a fixation member for anchoring the distalportion 28 of lead 20 at the targeted therapy delivery site. In someexamples, one or more of electrodes 30 may be a hook electrode or barbedelectrode to provide active fixation of the distal portion 28 of lead 20at the therapy delivery site.

Lead 20 may include one or more fixation members 32 for minimizing thelikelihood of lead migration. In the example of FIG. 2, fixation members32 are illustrated as triangle shaped. For example, fixation members 32,in the example of FIG. 2, may initially lay flat against lead body 22.As fixation members 32 are deployed, fixation members 32 extend outwardas illustrated in FIG. 2. For instance, a first fixation member 32 maybe include a first connection point 35A and a second connection point35B to connect the first fixation member 32 to lead body 22. In someexamples, first connection point 35A and second connection point 35B maybe connected to respective collars, described in FIGS. 6A-6D, that areslidable along lead body 22. One collar, but not necessary the collarsfor first connection point 35A and second connection point 35B, may notbe slidable.

As the collars are moved distally (e.g., towards electrodes 30),fixation members 32 extend outward. In some examples, such as theexample illustrated in FIG. 2, fixation members 32 are bow-like membersthat extend outwards. For instance, in FIG. 2, fixation members 32 formtriangle-like shapes when extend outwards. When the collars fully moveddistally (e.g., as far as the collars are configured to move), fixationmembers 32 may define a peak. For example, the first fixation member 32defines a peak 33. Peak 33 may be a point along fixation member 32having a tangent line that is parallel with lead body 22. To form peak33, there may be joint on fixation member 32 that is approximately inthe middle of first connection point 35A and second connection point35B. The joint moves outward in response to movement of the collars.

In some examples, a ray that extends from a point in the middle (i.e.,half-way) of first connection point 35A and second connection point 35B,along lead body 22 and is substantially perpendicular to lead body 22may intersect peak 33 (e.g., as illustrated by the dashed line).Substantially perpendicular may be in range of 75° to 105°.

Although FIG. 2 illustrates fixation members 32 as triangle-like shaped,the examples are not so limited. In some examples, fixation members 32may be lobe-like shaped. In general, fixation members 32 may be bow-likemembers that extend outward in response to being deployed. Examples ofthe bow-like members include lobe-like members, triangle-like members,and arc-like members. In these examples, the bow-like members include afirst connection point (e.g., like first connection point 35A) to afirst collar and a second connection point (e.g., like second connectionpoint 35B) to a second collar. When a pushing force, or possibly apulling force, is applied to the bow-like members to deploy the bow-likemembers, the bow-like members define a peak between the first connectionpoint and the second connection point. In some examples, the location ofthe peak may be at a half-way point between the first and secondconnection points. For instance, a ray extending from the half-way pointbetween the first and second connection points that is substantiallyperpendicular to lead body 22 intersects the peak.

Fixation members 32 are shown as bow-like members (e.g., triangle-likeshaped) in FIG. 2. However, there are other examples of fixation members32. That is, at least one of fixation members 32 may be a bow-likemember, and the remainder fixation members 32 may be bow-like or othershapes.

For example, fixation members 32 may include multiple sets of tineswhich engage the surrounding tissue when lead distal portion 28 ispositioned at the target therapy delivery site. The tines of fixationmember 32 may extend radially outward and proximally at an anglerelative to the longitudinal axis of lead body 22 to prevent or reduceretraction of lead body 22. For instance, the tines may include springsthat in an uncompressed state extend the tines outwards. Tines offixation member 32 may be collapsible against lead body 22 when lead 20is held within the confines of a lead delivery tool (e.g., a needle orintroducer) used to deploy lead distal portion 28 at the target implantsite. Upon removal of the lead delivery tool, the tines of fixationmember 32 may spread to a normally extended position (e.g., due to thespring bias) to engage with surrounding tissue and resist proximal andlateral migration of lead body 22. For instance, the tines may benormally biased to the extended position but retracted against theintroducer for implantation. When the introducer is removed, the tinesextend outward to their uncompressed state. Examples of the tines forfixation members 32 include tines 31 of FIG. 1. In some examples,fixation member 32 may additionally or alternatively include one or morehooks, barbs, helices, or other fixation mechanisms (e.g., bow-likemembers) extending from one or more longitudinal locations along leadbody 22 and/or lead distal end 26.

In some examples, the tines, when deployed, may be forward facing and/orbackward facing. Forward facing means that the portion of the tines thatare more proximate to proximal end 24 spread out when deployed. Forinstance, the tine has a connection point on lead body 22 and a free armof the tine that extends away from the lead body 22, and the portion ofthe free arm that is more proximate to proximal end 24 extends. Backwardfacing means that the portion of the tines that are more proximate todistal end 26 spread out when deployed. For instance, the tine has aconnection point on lead body 22 and a free arm of the tine that extendsaway from the lead body 22, and the portion of the free arm that is moreproximate to distal end 26 extends. Having both forward and backwardfacing tines may reduce lateral and proximal migration.

Other examples of fixation members 32 include bow-like members 29A and29B of FIG. 1. As described above, bow-like members 29A and 29B may belocated at proximal end 24 of lead body 22 (e.g., the elongated memberof lead 20) and may be implanted within tissue of tongue 40. In someexamples, bow-like members 29A and 29B, when deployed, each definerespective peaks between respective connection points of bow-likemembers 29A and 29B. The peak may be the outward most part of bow-likemembers 29A and 29B. For instance, a ray (e.g., hypothetical line)extending from lead body 22 and substantially perpendicular to lead body22 intersects the peak.

In general, the one or more fixation members 32 may include at least onefixation member that is a bow-like member. The bow-like member may beimplanted in tissue of tongue 40 and includes a first connection pointand a second connection point to respective collars located along thelongitudinal axis of lead body 22 (e.g., elongated member). As thecollars move distally, the bow-like member extend outward from lead body22 and defines a peak between the first connection point and the secondconnection point. For example, the peak may be halfway between the firstconnection point and the second connection point and extend outward fromlead body 22 so that the bow-like member forms an arc, triangle, or lobeas few examples.

Fixation members 32 may partially or wholly engage one or more ofprotrusor muscles 42 and/or 46 and/or other muscles below tongue 40,and/or other soft tissues of the neck (e.g., fat and connective tissue),when proximal end of lead body 20 is tunneled to an implant pocket ofIMD 16. In some examples, fixation member 32 may include one or morefixation mechanisms located at other locations, including at orproximate to distal end 26, between electrodes 30, or otherwise moredistally or more proximally than the location shown in FIG. 2.

The implant pocket of IMD 16 may be in a pectoral region of patient 14.Lead body 22 may include proximal connectors that engage with connectorassembly 17 of IMD 16. Accordingly, the length of the elongated leadbody 22 from distal portion 28 to the lead proximal end 24 may beselected to extend from a target therapy delivery site in protrusormuscles 42 and/or 46 to a location in the pectoral region where IMD 16is implanted. The length of lead body 22 (e.g., elongated member) may beup to 10 cm or up to 20 cm as examples but may generally be 25 cm orless, though longer or shorter lead body lengths may be used dependingon the anatomy and size of patient 14.

FIG. 3 is a conceptual diagram illustrating example locations of motorpoints where stimulation for OSA therapy may be delivered. FIG. 3illustrates jaw 50 of patient 14, where patient 14 is in a supineposition and jaw 50 of patient 14 is viewed from an inferior location ofpatient 14. For instance, FIG. 3 illustrates symphysis 51 and hyoid bone52. In the example illustrated in FIG. 3, the line interconnectingsymphysis 51 and hyoid bone 52 may be considered as a y-axis along themidline of tongue 40. FIG. 3 also illustrates intergonial distance 53between the two gonia of patient 14, where the gonia is a point on eachside of the lower jaw 50 at the mandibular angle. Intergonial distance53 may be along the x-axis of tongue 40.

FIG. 3 illustrates motor points 54A and 54B and motor points 55A and55B. Motor points 54A may be motor points for the right genioglossusmuscle, and motor points 54B may be motor points for the leftgenioglossus muscle. Motor points 55A may be motor points for the rightgeniohyoid muscle, and motor points 55B may be motor points for the leftgeniohyoid muscle. Motor points 54A and 54B and motor points 55A and 55Bmay genericize the motor points for each muscle for purposes ofillustration. There may be additional motor points and/or motor pointsat different locations for each muscle.

In one or more examples, lead 20 and/or one or more electrodes 30 may beimplanted proximate to motor points 54A, 54B, 55A, or 55B forstimulating at motor points 54A, 54B, 55A, and/or 55B. For instance, inexamples where two leads are implanted, a first lead and its electrodesmay be implanted proximate to motor points 54A and/or 55A and a secondlead and its electrodes may be implanted proximate to motor points 54Band/or 55B. In one or more examples, electrodes 30 may be approximately1 mm to 10 mm from respective motor points 54A, 54B, 55A, or 55B.

A hypoglossal nerve (e.g., on the left or right side of tongue 40)initially is a trunk of nerves fibers called axons. The axons of thehypoglossal nerve branch out. For example, the trunk of hypoglossalnerve includes multiple sets of axons including a first set of axons,and the first set of axons branch out from the trunk of the hypoglossalnerve. The first set of axons include multiple groups of axons includinga first group of axons, and the first group of axons branch out from thefirst set of axons, and so forth. The locations where the branched-outaxons interface with respective muscle fibers of protrusor muscles 42and/or 46 (e.g., genioglossus and/or geniohyoid muscle) are referred toas motor points.

For instance, a branch of the hypoglossal nerve that interfaces (e.g.,connects at the neuro-muscular junction) with the muscle fiber isreferred to as a terminal branch, and the end of the terminal branch isa motor point. The length of a terminal branch may be approximately 10mm from the hypoglossal nerve to the genioglossal or geniohyoid muscles.In some examples, there may be approximately an average of 1.5 terminalbranches with a standard deviation of ±0.7 for the right geniohyoidmuscle, an average of 4.8 terminal branches with a standard deviation of±1.4 for the right genioglossus muscle, an average of 2.0 terminalbranches with a standard deviation of ±0.9 for the left geniohyoidmuscle, and an average of 5.1 terminal branches with a standarddeviation of ±1.9 for the left genioglossus muscle.

There may be possible advantages with stimulating at motor points 54A,54B, 55A, or 55B, as compared to some other techniques. For instance,some techniques utilize cuff electrodes or stimulate at the hypoglossalnerve. Due to the different bifurcation patterns, placing a cuffelectrode around the hypoglossal nerve, or generally attaching anelectrode to the hypoglossal nerve can be challenging. Also, where cuffelectrodes or electrodes that attach to the hypoglossal nerve are used,implanting electrodes around or at each of the hypoglossal nervesrequires multiple surgical entry points to attached to both hypoglossalnerves. Moreover, utilizing cuff electrodes or electrodes that attach tothe hypoglossal nerves can possibly negatively impact the nerve bytugging, stretching, or otherwise causing irritation. Accordingly,utilizing lead 20 and electrodes 30 that are implanted proximate to themotor points may be beneficial (e.g., less surgery to implant and lessimpact on the nerve) as compared to techniques where cuff electrodes orelectrodes implanted on the hypoglossal nerve are utilized.

Furthermore, stimulating at motor points 54A, 54B, 55A, and/or 55B, suchas at the bifurcation point of a motor neuron that attach to musclefibers, may provide advantages such as for better control of musclemovement. Because motor points 54A, 54B, 55A, and 55B are spatiallydistributed, by stimulating motor points 54A, 54B, 55A, and/or 55B, theamount of the genioglossus and geniohyoid muscle that is beingstimulated can be controlled. Also, stimulating at motor points 54A,54B, 55A, and/or 55B may allow for more gentle muscle activation. Forinstance, when stimulation is provided near the trunk of the hypoglossalnerve, even stimulation signal with relatively small amplitude can causethe genioglossus and/or geniohyoid muscle to fully protrude (e.g., thereis high loop gain where small stimulation amplitudes cause large muscleprotrusion). Fine tuning of how much to protrude the genioglossus and/orgeniohyoid muscle may not be available when stimulating at a trunk ofthe hypoglossal nerve. However, there may be lower loop gain stimulatingat motor points 54A, 54B, 55A, and/or 55B. For instance, a stimulationsignal having a lower amplitude may move cause the genioglossus and/orgeniohyoid muscle to protrude a small amount, and a stimulation signalhaving a higher amplitude may move cause the genioglossus and/orgeniohyoid muscle to protrude a higher amount when stimulating at motorpoints 54A, 54B, 55A and/or 55B.

The following are example locations of motor points 54A, 54B, 55A, and55B relative to the midline (x-axis), posterior symphysis 51 (y-axis),and depth (z-axis), where the depth is from the plane formed by theinferior border of symphysis 51 and anterior border of hyoid bone 52.

Motor points 54A may be for the right genioglossus muscle and may belocated at 13.48 mm±3.59 from the x-axis, 31.01 mm±6.96 from the y-axis,and 22.58 mm±3.74 from the z-axis. Motor points 55A may be for the rightgeniohyoid muscle and may be located at 11.74 mm±3.05 from the x-axis,41.81 mm±6.44 from the y-axis, and 16.29 mm±3.40 from the z-axis. Motorpoints 54B may be for the left genioglossus muscle and may be located at9.96 mm±2.24 from the x-axis, 29.62 mm±9.25 from the y-axis, and 21.11mm±4.10 from the z-axis. Motor points 55B may be for the left geniohyoidmuscle and may be located at 11.45 mm±1.65 from the x-axis, 39.63mm±8.03 from the y-axis, and 15.09 mm±2.41 from the z-axis.

FIG. 4 is block diagram illustrating example configurations ofimplantable medical devices (IMDs) which may be utilized in the systemof FIG. 1. As shown in FIG. 4, IMD 16 includes sensing circuitry 56,processing circuitry 57, therapy delivery circuitry 58, switch circuitry59, memory 60, telemetry circuitry 61, and power source 62. IMD 16 mayinclude a greater or fewer number of components. For example, in someexamples, such as examples in which IMD 16 deliver the electricalstimulation in an open-loop manner, IMD 16 may not include sensingcircuitry 56.

Switch circuitry 59 may be configured to, in response to instructionsfrom processing circuitry 57, switch the coupling of electrodes 30between sensing circuitry 56 and therapy delivery circuitry 58. Inexamples where sensing circuitry 56 is not used, switch circuitry 59 maynot be needed. However, even in examples where sensing circuitry 56 isnot used, IMD 16 may include switch circuitry 59 such as to disconnectelectrodes 30 from therapy delivery circuitry 58.

In some examples, therapy delivery circuitry 58 may include a pluralityof regulated current sources or sinks, with each current source or sinkcoupled to one of electrodes 30. In such examples, therapy deliverycircuitry 58 may control each current source or sink and switchingbetween electrodes 30 may not be necessary for therapy delivery sinceeach one of electrodes 30 is individually controllable.

Although not shown in FIG. 3, in some examples, IMD 16 may include oneor more sensors configured to sense posture or position of patient 14.For example, IMD 16 may include accelerometer to determine if patient 14is lying down. Another example of the one or more sensors is a motionsensor, and movement sensed by the motion sensor may indicate if patient14 is having restless sleep, which may be indicative of the onset ofOSA. Additional examples of the sensors include acoustical sensors or amicrophone for detecting vibrations in upper airway 48. Vibrations inupper airway 48 may be indicative of the onset of OSA. In some examples,processing circuity 57 may control delivery of therapy based oninformation received from the one or more sensors, such as delivery oftherapy after sensing an onset of OSA.

In some examples, electrodes 30 may be configured to senseelectromyogram (EMG) signals. Sensing circuitry 56 may be switchablycoupled to electrodes 30 via switch circuitry 59 to be used as EMGsensing electrodes with electrodes 30 are not being used forstimulation. EMG signals may be used by processing circuitry 57 todetect sleep state and/or low tonal state of protrusor muscles 42 and/or46 for use in delivering electrical stimulation. In some examples,rather than using electrodes 30 or in addition to using electrodes 30,there may be other electrodes or sensors used to sense EMG signals.

In general, IMD 16 may comprise any suitable arrangement of hardware,alone or in combination with software and/or firmware, to perform thetechniques attributed to IMD 16 and processing circuitry 57, therapydelivery circuitry 58, and telemetry circuitry 61 of IMD 16. In variousexamples, IMD 16 may include one or more processors, such as one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field programmable gate arrays (FPGAs), orany other equivalent integrated or discrete logic circuitry, as well asany combinations of such components.

The various units of IMD 16 may be implemented as fixed-functioncircuits, programmable circuits, or a combination thereof.Fixed-function circuits refer to circuits that provide particularfunctionality, and are preset on the operations that can be performed.Programmable circuits refer to circuits that can be programmed toperform various tasks, and provide flexible functionality in theoperations that can be performed. For instance, programmable circuitsmay execute software or firmware that cause the programmable circuits tooperate in the manner defined by instructions of the software orfirmware. Fixed-function circuits may execute software instructions(e.g., to receive parameters or output parameters), but the types ofoperations that the fixed-function circuits perform are generallyimmutable. In some examples, one or more of the units may be distinctcircuit blocks (fixed-function or programmable), and in some examples,one or more of the units may be integrated circuits.

IMD 16 may include arithmetic logic units (ALUs), elementary functionunits (EFUs), digital circuits, analog circuits, and/or programmablecores, formed from programmable circuits. In examples where theoperations of IMD 16 are performed using software executed by theprogrammable circuits, memory 60 may store the instructions (e.g.,object code) of the software that processing circuitry 57 receives andexecutes, or another memory within IMD 16 (not shown) may store suchinstructions.

IMD 16 also, in various examples, may include a memory 60, such asrandom access memory (RAM), read only memory (ROM), programmable readonly memory (PROM), erasable programmable read only memory (EPROM),electronically erasable programmable read only memory (EEPROM), flashmemory, comprising executable instructions for causing the one or moreprocessors to perform the actions attributed to them. Moreover, althoughsensing circuitry 56, processing circuitry 57, therapy deliverycircuitry 58, switch circuitry 59, and telemetry circuitry 61 aredescribed as separate circuitry, in some examples, sensing circuitry 56,processing circuitry 57, therapy delivery circuitry 58, switch circuitry59, and telemetry circuitry 61 are functionally integrated. In someexamples, sensing circuitry 56, processing circuitry 57, therapydelivery circuitry 58, switch circuitry 59, and telemetry circuitry 61correspond to individual hardware units, such as ASICs, DSPs, FPGAs, orother hardware units.

Memory 60 stores therapy programs 63 (also called stimulation programs63) that specify stimulation parameter values for the electricalstimulation provided by IMD 16. Memory 60 may also store instructionsfor execution by processing circuitry 57, in addition to stimulationprograms 63. Information related to sensed parameters of patient 14(e.g., from sensing circuitry 56 or the one or more sensors of IMD 16)may be recorded for long-term storage and retrieval by a user, and/orused by processing circuitry 57 for adjustment of stimulation parameters(e.g., amplitude, pulse width, and pulse rate). In some examples, memory60 includes separate memories for storing instructions, electricalsignal information, and stimulation programs 63. In some examples,processing circuitry 57 may select new stimulation parameters for astimulation program 63 or new stimulation program from stimulationprograms 63 to use in the delivery of the electrical stimulation basedon patient input and/or monitored physiological states after terminationof the electrical stimulation.

Generally, therapy delivery circuitry 58 generates and deliverselectrical stimulation under the control of processing circuitry 57. Insome examples, processing circuitry 57 controls therapy deliverycircuitry 58 by accessing memory 60 to selectively access and load atleast one of therapy programs 63 to therapy delivery circuitry 58. Forexample, in operation, processing circuitry 57 may access memory 60 toload one of stimulation programs 63 to therapy delivery circuitry 58.

By way of example, processing circuitry 57 may access memory 60 to loadone of stimulation programs 63 to control therapy delivery circuitry 58for delivering the electrical stimulation to patient 14. A clinician orpatient 14 may select a particular one of stimulation programs 63 from alist using a programming device, such as a patient programmer or aclinician programmer. Processing circuitry 57 may receive the selectionvia telemetry circuitry 61. Therapy delivery circuitry 58 delivers theelectrical stimulation to patient 14 according to the selected programfor an extended period of time, such as minutes or hours while patient14 is asleep (e.g., as determined from the one or more sensors and/orsensing circuitry 56). For example, processing circuitry 57 may controlswitch circuitry 59 to couple electrodes 30 to therapy deliverycircuitry 58.

Therapy delivery circuitry 58 delivers electrical stimulation accordingto stimulation parameters. In some examples, therapy delivery circuitry58 delivers electrical stimulation in the form of electrical pulses. Insuch examples, relevant stimulation parameters may include a voltage orcurrent pulse amplitude, a pulse rate, a pulse width, a duty cycle,and/or the combination of electrodes 30 that therapy delivery circuitry58 uses to deliver the stimulation signal. In some examples, therapydelivery circuitry 58 delivers electrical stimulation in the form ofcontinuous waveforms. In such examples, relevant stimulation parametersmay include a voltage or current amplitude, a frequency, a shape of thestimulation signal, a duty cycle of the stimulation signal, or thecombination of electrodes 30 therapy delivery circuitry 58 uses todeliver the stimulation signal.

In some examples, the stimulation parameters for the stimulationprograms 63 may be selected to cause protrusor muscles 42 and/or 46 to aprotruded state (e.g., to open-up airway 48). An example range ofstimulation parameters for the electrical stimulation that are likely tobe effective in treating OSA (e.g., upon application to the hypoglossalnerves to cause protrusor muscles 42, 46 to protrude or upon applicationto motor points such as motor points 54A, 54B, 55A, and 55B), are asfollows:

-   -   a. Frequency or pulse rate: between about 30 Hz and about 50 Hz.        In some examples, the minimum target frequency is used which can        achieve muscle tetany (e.g., constant contraction) and provide        the required force to open the airway.    -   b. Current Amplitude: between about 0.5 milliamps (mA) and about        10 mA, and more generally from 0.5 mA to 3 mA, and approximately        1.5 mA.    -   c. Pulse Width: between about 100 microseconds (μs) and about        500 μs. In some examples, a pulse width of 150 μs might be used        for reduced power consumption. In some particular examples, the        pulse width is approximately 210 μs. In some cases, shorter        pulse widths may be used in conjunction with higher current or        voltage amplitudes.

Processing circuitry 57 may select stimulation programs 63 foralternating delivery of electrical stimulation between stimulating theleft protrusor muscles 42 and/or 46 and the right protrusor muscles 42and/or 46 on a time basis, such as in examples where two leads 20 areimplanted. In some examples, there may be some overlap in the deliveryof electrical stimulation such that for some of amount of time both leftand right protrusor muscles 42 and/or 46 are being stimulated. In someexamples, there may be a pause in alternating stimulation (e.g.,stimulate left protrusor muscles, a time period with no stimulation,then stimulate right protrusor muscles, and so forth). Processingcircuitry 57 may also select stimulation programs 63 that select betweendifferent combinations of electrodes 30 for stimulating, such as tostimulate different locations of the hypoglossal nerve(s), which mayhelp with fatigue as well as provide more granular control of how muchto protrude tongue 40.

In the example of FIG. 4, therapy delivery circuitry 58 driveselectrodes 30 of lead 20. Specifically, therapy delivery circuitry 58delivers electrical stimulation (e.g., regulated current or voltagepulses at pulse rates and pulse widths described above) to tissue ofpatient 14 via selected electrodes 30A-30D carried by lead 20. Aproximal end of lead 20 extends from the housing of IMD 16 and a distalend of lead 20 extends to a target therapy site, such as one or bothhypoglossal nerves and/or motor points 54A, 55A, 54B, and/or 55B.Therapy delivery circuitry 54 may deliver electrical stimulation withelectrodes on more than one lead and each of the leads may carry one ormore electrodes, such as when patient 14 is implanted with two leads 20in tongue 40 for stimulating both hypoglossal nerves simultaneously orbilaterally (e.g., one after the other) or both motor points 54A and 54Band/or motor points 55A and 55B. The leads may be configured as an axiallead with ring electrodes or segmented electrodes and/or paddle leadswith electrode pads arranged in a two-dimensional array. The electrodesmay operate in a bipolar or multi-polar configuration with otherelectrodes, or may operate in a unipolar configuration referenced to anelectrode carried by the device housing or “can” of IMD 16.

In this way, the example of FIG. 4 may be considered as a system fordelivering electrical stimulation therapy that includes lead 20 fordelivering electrical stimulation therapy. Rather than lead 20 or inaddition to lead 20, in some examples, lead 90, described in more detailwith respect to FIGS. 6A-6D, may be utilized. Whether lead 20 or lead 90is used, the lead includes an elongated member (e.g., lead body 22 orelongated member 93 of FIGS. 6A-6D) defining a longitudinal axis andincluding a proximal end and a distal end. The lead also includes one ormore electrodes disposed at the distal end of the elongated member andone or more fixation members (e.g., fixation members 32 or fixationmembers 100A-100F described with FIGS. 6A-6D).

The distal end of the elongated member is implanted in tongue 40 ofpatient 14 such that the one or more electrodes are implanted proximateto one or more motor points (e.g., motor points 54A, 54B, 55A, and/or55B) of a protrusor muscle (e.g., at least one of the genioglossus orgeniohyoid muscle) of tongue 40 of patient 14 and at least one fixationmember of the one or more fixation members is a bow-like member that isimplanted within tissue of tongue 40. At least one fixation member, whendeployed, includes a peak between connection points of the bow-likemember.

A medical device (e.g., IMD 16) may include connector assembly 17configured to couple to the proximal end of the elongated member of thelead. The medical device may be configured to deliver electricalstimulation therapy via the one or more electrodes that cause at leastone of the genioglossal or geniohyoid muscle (e.g., protrusor muscles 42and/or 46) to protrude tongue 40 of patient 14.

In the above example, the medical device is coupled to one lead (e.g.,lead 20 or lead 90, described below). However, the example techniquesare not so limited. In some examples, patient 14 may be implanted withtwo leads, where a first lead is for stimulating a first set of motorpoints (e.g., motor points 54A and/or 55A) of a first protrusor muscleof tongue 40 and the second lead is for stimulating a second set ofmotor points (e.g., motor points 54B and/or 55B) of a second protrusormuscle of tongue 40. One or both of the first and second leads may besimilar to leads 20 and 90. For example, the second lead may include asecond elongated member defining a second longitudinal axis including asecond proximal end and a second distal end, a second set of one or moreelectrodes disposed at the distal end of the second elongated member,and a second set of one or more fixation members.

The second distal end of the second elongated member is implanted intongue 40 of patient 14 such that the one or more electrodes areimplanted proximate to a second set of motor points of a secondprotrusor muscle within tongue 40 of patient 14 and at least onefixation member of the second set of one or more fixation members isimplanted within tissue of tongue 40, and at least one fixation memberof the second set of one or more fixation members, when deployed,defines a peak between connection points of the connection points of theat least one fixation member (e.g., a bow-like member).

In some examples, processing circuitry 57 may control therapy deliverycircuitry 58 to deliver or terminate the electrical stimulation based onpatient input received via telemetry circuitry 61. Telemetry circuitry61 includes any suitable hardware, firmware, software or any combinationthereof for communicating with another device, such as an externalprogrammer. Under the control of processing circuitry 57, telemetrycircuitry 61 may receive downlink telemetry (e.g., patient input) fromand send uplink telemetry (e.g., an alert) to a programmer with the aidof an antenna, which may be internal and/or external. Processingcircuitry 57 may provide the data to be uplinked to the programmer andthe control signals for telemetry circuitry 61 and receive data fromtelemetry circuitry 61.

Generally, processing circuitry 57 controls telemetry circuitry 61 toexchange information with a medical device programmer and/or anotherdevice external to IMD 16. Processing circuitry 57 may transmitoperational information and receive stimulation programs or stimulationparameter adjustments via telemetry circuitry 61. Also, in someexamples, IMD 16 may communicate with other implanted devices, such asstimulators, control devices, or sensors, via telemetry circuitry 61.

Power source 62 delivers operating power to the components of IMD 16.Power source 62 may include a battery and a power generation circuit toproduce the operating power. In some examples, the battery may berechargeable to allow extended operation. Recharging may be accomplishedthrough proximal inductive interaction between an external charger andan inductive charging coil within IMD 16. In other examples, an externalinductive power supply may transcutaneously power IMD 16 wheneverelectrical stimulation is to occur.

FIG. 5 is a block diagram illustrating an example configuration of anexternal programmer 70. While programmer 70 may generally be describedas a hand-held computing device, the programmer may be a notebookcomputer, a cell phone, or a workstation, for example. As illustrated inFIG. 5, external programmer 70 may include processing circuitry 72,memory 74, user interface 76, telemetry circuitry 78, and power source80.

In general, programmer 70 comprises any suitable arrangement ofhardware, alone or in combination with software and/or firmware, toperform the techniques attributed to programmer 70, and processingcircuitry 72, user interface 76, and telemetry module 78 of programmer70. Examples of processing circuitry 72 may include one or moreprocessors, such as one or more microprocessors, DSPs, ASICs, FPGAs, orany other equivalent integrated or discrete logic circuitry, as well asany combinations of such components. Examples of memory 74 include RAM,ROM, PROM, EPROM, EEPROM, flash memory, a hard disk, a CD-ROM,comprising executable instructions for causing the one or moreprocessors to perform the actions attributed to them. Moreover, althoughprocessing circuitry 72 and telemetry circuitry 78 are described asseparate circuitry, in some examples, processing circuitry 72 andtelemetry circuitry 78 are functionally integrated. In some examples,processing circuitry 72 and telemetry circuitry 78 correspond toindividual hardware units, such as ASICs, DSPs, FPGAs, or other hardwareunits.

In some examples, memory 74 may further include program information(e.g., stimulation programs) defining the electrical stimulation,similar to those stored in memory 60 of IMD 16. The stimulation programsstored in memory 74 may be downloaded into memory 60 of IMD 16.

User interface 76 may include a button or keypad, lights, a speaker forvoice commands, a display, such as a liquid crystal (LCD),light-emitting diode (LED), or cathode ray tube (CRT). In some examplesthe display may be a touch screen. As discussed in this disclosure,processing circuitry 72 may present and receive information relating toelectrical stimulation and resulting therapeutic effects via userinterface 76. For example, processing circuitry 72 may receive patientinput via user interface 76. The input may be, for example, in the formof pressing a button on a keypad or selecting an icon from a touchscreen.

Processing circuitry 72 may also present information to the patient inthe form of alerts related to delivery of the electrical stimulation topatient 14 or a caregiver via user interface 76. Although not shown,programmer 70 may additionally or alternatively include a data ornetwork interface to another computing device, to facilitatecommunication with the other device, and presentation of informationrelating to the electrical stimulation and therapeutic effects aftertermination of the electrical stimulation via the other device.

Telemetry circuitry 78 supports wireless communication between IMD 16and programmer 70 under the control of processing circuitry 72.Telemetry circuitry 78 may also be configured to communicate withanother computing device via wireless communication techniques, ordirect communication through a wired connection. In some examples,telemetry circuitry 78 may be substantially similar to telemetrycircuitry 61 of IMD 16 described above, providing wireless communicationvia an RF or proximal inductive medium. In some examples, telemetrycircuitry 78 may include an antenna, which may take on a variety offorms, such as an internal or external antenna.

Examples of local wireless communication techniques that may be employedto facilitate communication between programmer 70 and another computingdevice include RF communication according to the 802.11 or Bluetoothspecification sets, infrared communication (e.g., according to the IrDAstandard), or other standard or proprietary telemetry protocols. In thismanner, other external devices may be capable of communicating withprogrammer 70 without needing to establish a secure wireless connection.

Power source 80 delivers operating power to the components of programmer70. Power source 80 may include a battery and a power generation circuitto produce the operating power. In some examples, the battery may berechargeable to allow extended operation.

FIGS. 6A-6D are conceptual diagrams illustrating deployment of fixationmembers. For example, FIGS. 6A-6D illustrate an example of lead 90 thatincludes elongated member 93 (e.g., lead body) defining a longitudinalaxis 92 and includes proximate end 96 and distal end 94. In the exampleof FIGS. 6A-6D, one or more electrodes 98A and 98B are disposed atdistal end 94, and one or more proximal contacts 99A and 99B aredisposed at proximal end 96 for connection to IMD 16. In some examples,there may be a 1 mm spacing between electrode 98A and distal end 94, and“disposed at distal end 94” includes examples where the one or moreelectrodes 98A and 98B are proximate to distal end 94.

As illustrated in FIGS. 6A-6D, lead 90 includes one or more fixationmembers 100A-100F. Fixation members 100A-100F may be in an undeployedstate, where fixation members 100A-100F rest generally flat in anundeployed (i.e., retracted) state along elongated member 93, asillustrated in FIG. 6A. As described in more detail below, FIG. 6Billustrates fixation members 100A-100F in a first partially deployed(i.e., partially extended) state, and FIG. 6C illustrates fixationmembers 100A-100F in a second partially deployed (i.e., partiallyextended) state. FIG. 6D illustrates fixation members 100A-100F in afully deployed state (i.e., fully extended). As described in moredetail, fixation members 100A-100F may be bow-like members that can beselectively extended from a flat configuration, to an arc-likeconfiguration, to a triangle-like configuration, and ultimately to alobe-like configuration, and retracted from the lobe-like configuration,to a triangle-like configuration, to the arc-like configuration, and tothe flat configuration.

As illustrated in FIGS. 6A-6D, lead 90 includes one or more collars101A-101D. Each one of collars 101A-101D forms a connection point for atleast one of fixation members 100A-100F. Collars 101A-101D and fixationmembers 100A-100F may be formed from polyurethane, silicone,polytetrafluoroethylene (PTFE), silicone rubber, nylon, polyethyleneterephthalate (PET), latex, thermoplastic elastomers and polyimides, asa few examples. Collars 101A-101D may be spaced apart by approximately 4mm (e.g., with range of 2 mm and 6 mm). In some examples, collars101A-101D may have a size that is approximately ⅓ the diameter of lead90, but smaller and larger sizes are possible.

In some examples, the most distal collar (e.g., collar 101A) may befixed in location (e.g., formed part of elongated member 93, welded orepoxied, as a few examples) on elongated member 93. The other collars(e.g., collars 101B-101D) may be slidable along elongated member 93. Forexample, as illustrated in FIG. 6A, collar 101A may form a firstconnection point for fixation members 100A and 100D and collar 101B mayform a second connection point for fixation members 100A and 100D.Collar 101B may form a first connection point for fixation members 100Band 100E and collar 101C may form a second connection point for fixationmembers 100B and 100E. Collar 101C may form a first connection point forfixation members 100C and 100F and collar 101D may form a secondconnection point for fixation members 100C and 100F. Each of fixationmembers 100A-100F may be welded, bonded, or epoxied to respective onesof collar 101A-101D to connect to respective ones of collar 101A-101D.

Accordingly, in the example illustrated in FIGS. 6A-6D, collars101A-101D are connected in series through respective fixation members100A-100F. For example, collar 101A is connected to collar 101B throughfixation members 100A and 100D, collar 101B is connected to collar 101Cthrough fixation members 100B and 100E, and collar 101C is connected tocollar 101D through fixation members 100C and 100F. Because collar 101Amay be fixed in position on elongated member 93, collars 101B-101D areable to remain along the side of elongated member 93.

As described in more detail below, in some examples, when a longitudinalcompression (e.g., pushing) force is applied to the most proximal collar(e.g., collar 101D), all fixation members 100A-100F have the same forceexerted on them because fixation members 100A-100F are in series witheach other. There may be some additional frictional forces or externalforces from tissue when lead 90 is implanted causing the force exertedon each of fixation members 100A-100F to be different. However, suchadditional forces may be relatively minimal.

When a pushing force is applied to collar 101D, collars 101B-10D allmove distally. As described above, collar 101A may be fixed in position.The movement of collars 101B-101D causes respective fixation members100A-100F to bow outwards from elongated member 93. For instance, distalmovement along elongated member 93 of collars 101D and 101C causefixation members 100C and 100F to bow outwards, distal movement alongelongated member 93 of collars 101C and 101B cause fixation members 100Band 100E to bow outwards, and distal movement along elongated member 93of collar 101B with collar 101A being in fixed position causes fixationmembers 100A and 100D to bow outwards.

The amount that fixation members 100A-100F (also called bow-like members100A-100F) bow outward may be based on the amount of distal movement ofcollars 101A-101D. For instance, FIGS. 6B-6D illustrate differentamounts of movement of collars 101A-101D based on the different amountof distal movement of collars 101A-101D.

FIGS. 6B and 6C may be considered as illustrating fixation members100A-100F in intermediate deployed states with the example illustratedin FIG. 6D being the final deployed state of fixation members 100A-100F.However, in some examples, the examples illustrated in FIGS. 6B or 6Cmay be the final deployed state of fixation members 100A-100F. As oneexample, there may be one or more flanges or protrusions on elongatedmember 93 that stop how far distally collars 101B-101D can move. Otherways to limit the movement of collar 101B-101D are possible.

Once fixation members 100A-100F are deployed, the tissue from tongue 40may provide sufficient friction so that collars 101B-101D do not move.Then, as scar tissue begins to form around and through the deployedfixation members 100A-100F, lead 90 may remain in place and collars101B-101D may remain in place. In some examples, it may be possible toglue (e.g., surgical adhesive) or lock collars 101B-101D in place (e.g.,deploy flanges on elongated member 93 to stop movement of collars101B-101D along longitudinal axis 92 of elongated member 93) afterfixation members 100A-100F are deployed to stop movement of collars101B-101D until sufficient scarring tissue forms to hold lead 90 andcollars 101B-101D in place.

FIGS. 6A-6D illustrate one example shape of fixation members 100A-100D.However, the techniques are not so limited. For instance, collars101A-101D may be spaced apart at different distances so that the amountby which one of the fixation members 100A-100D bows out is differentthan the amount by which another one of the fixation members 100A-100Dbows out. Also, in additional to fixation members 100A-100D that arebow-like fixation members, lead 90 may include tines (forward and/orbackward facing) as fixation member.

As described above, one way to deploy fixation members 100A-100F is byapplying a compression force to collar 101D. There may be various waysin which fixation members 100A-100F may transition from the undeployedstate of FIG. 6A, through the first and second partially deployed statesof FIGS. 6B and 6C, and to the fully deployed state of FIG. 6D, or tothe deployed states of FIGS. 6B or 6C, where the deployed states ofFIGS. 6B or 6C are the final, fully deployed state. As one example, theintroducer used to implant lead 90 into tongue 40 may hold fixationmembers 100A-100F along elongated body 93. As the introducer is removed,fixation members 100A-100F expand out to the deployed state. Forexample, fixation members 100A-100F have a spring bias to naturally bein the deployed state illustrated in FIG. 6D. The introducer holdsfixation members 100A-100F in the undeployed state and as the introduceris removed fixation members 100A-100F move to the deployed state due tothe spring bias.

As another example, once lead 90 is secured in place, a push tubing maybe used to push on collar 101D, and the force from the push tubingcauses fixation members 100A-100F to deploy. In some examples, the pushtubing may have a hydrophilic coating on the inner surface. Uponexposure to body fluids, the coating is hydrated, minimizing frictionbetween the push tubing and the internal insulation of lead 90 to alloweasier deployment of fixation members 100A-100F.

In some examples, the push tubing may be the introducer. For example,the introducer may initially cover fixation members 100A-100F, and thenthe introducer is pulled back proximally beyond collar 101D to exposefixation members 100A-100F. Then, the introducer is pushed distally andpushes collar 101D (e.g., applies a compression force to collar 101D),which compresses fixation members 100A-100F, and causes fixation members100A-100F to extend. For instance, the introducer is first pulled backbeyond collar 101D, and then rubs up against elongated member 93. As theintroducer is moved distally along elongated member 93, the introducermoves collar 101D distally and the fixation members 100A-100F extendperpendicular to elongated member 93 since the introducer pushes up oncollar 101D.

In this way, at least one fixation member of fixation members 100A-100Fmay be configured to deploy in response to movement of an introducerused for lead implantation. For example, the at least one fixationmember of fixation members 100A-100F may be configured to deploy inresponse to the introducer pushing on the at least collar via elongatedmember 93 causing the at least one fixation member to distendperpendicular to lead 90.

The introducer may be an open grid and have “windows” that allowelectrodes 98A and 98B on lead 90 to be exposed when lead 90 is evenwith the end of the introducer. In this way, the introducer does nothave to be withdrawn to expose electrodes 98A and 98B, allowing fortesting to ensure that lead 90 is properly placed before deployment ofthe fixation members 100A-100F. Having such windows in the introducermay reduce the chance of inadvertently deploying one or more fixationmembers 100A-100F during the testing to ensure proper lead placement.

As illustrated, in some examples, collar 101D includes opening 108. Insome examples, a hook of a pushing device may be used to hook intoopening 108. The surgeon may then push the pushing device distallycausing collar 101D to move distally and apply the compression pressureto extend fixation members 100A-100F outward. In some examples, opening108 may be used with a pulling device, which may be the same as thepushing device, to retract fixation members 100A-100F, as describedbelow.

There may be more or fewer fixation members 100A-100F than illustratedin FIGS. 6A-6D. For ease of illustration, in FIGS. 6A-6D, fixationmembers 100A-100F are illustrated as being deployed along the x-axis,where the y-axis defines the longitudinal axis. In some examples, theremay be additional fixation members that are deployed along the z-axis(e.g., fixation members like fixation members 100A-100F may extend attwo points, three points, or four or more points around elongated member93). For instance, there may be a plurality of fixation members locatedradially around elongated member 93. In some examples, the fixationmembers may be separated by approximately 90°.

As illustrated in FIG. 6D, when deployed, at least one fixation memberof fixation members 100A-100F includes a peak 102 that is substantiallyperpendicular to longitudinal axis 92 of elongated member 93 of lead 90,and represents the radially outermost portion of the fixation memberrelative to the longitudinal axis of elongated member 93. Peak 102 isillustrated in FIG. 6D to ease with illustration, and there arerespective peaks on other fixation members 100A-100F. Also, there is apeak for respective fixation members 100A-100F illustrated in FIGS. 6Band 6C. FIGS. 7A-7C illustrate the example of peaks in further detail.

As one example, peak 102 refers to a location on fixation member100A-100F having at least two connections back to respective collars101A-101D, where the tangent line at peak 102 is parallel to lead 90(e.g., longitudinal axis 92). For example, peak 102 is on fixationmember 100E having a first connection point on collar 101A and a secondconnection point on collar 101B. Peak 102 may be a point of fixationmember 100E that is furthest from elongated member 93 (e.g., an outwardmost bend of fixation member 100E). A tangent line at the point of peak102 may be parallel with longitudinal axis 92. Further, a line extendingfrom peak 102 to elongated member 93 may be substantially perpendicularto longitudinal axis 92 and intersect elongated member 93 substantiallymidway between the first connection point and the second connectionpoint. As noted above, FIGS. 7A-7C further illustrates examples ofpeaks.

For example, in examples where one or more fixation members 100A-100Fare lobe shaped, as illustrated in FIG. 6D, peak 102 may be the highestpoint on the arc of the lobes. In such examples, there is an arc towardspeak 102, which forms one of the connections to collar 101B, and an arcaway from peak 102, which forms another of the connections to collar101A. In examples where one or more of fixation members 100A-100F aretriangular shaped, there may be two points respectively on two collars101A-101D that define a width of the triangle, and the third pointconnects to the two points and forms a peak, as illustrated by peak 33in FIG. 2. “Substantially perpendicular” means that a line extendingfrom the peak is within a range of 75° to 105°, and generally at 90°relative to the longitudinal axis of the elongated member 93 (e.g.,leady body) of lead 90.

A distance 104 between lead 90 and peak 102 of the at least one fixationmember of fixation members 100A-100F may be approximately 2 mm (e.g.,between a range of 1.5 mm and 2.5 mm). In some examples, the distance104 may be approximately twice the diameter of lead 90. Because lead 90is implanted in musculature of tongue 40, there would be eventual tissuescaring from the operation, which may scar around fixation members100A-100F that are extended outwards and embedded in or against thetissue. The tissue scarring may already provide some level of securinglead 90 in place (e.g., to minimize lead migration). Therefore, havinglarge sized fixation members may not be necessary. For example, byhaving fixation members 100A-100F extend approximately 2 mm outward fromlead 90, there may be sufficient anchoring of lead 90 to the musculatureto minimize lead migration as the bow-like members (e.g., arc-shaped,triangular-shaped, or lobe-shaped bow-like members embed in or bearagainst the tissue of tongue 40). Some other lead types, such as thoseimplanted intravenously, may require larger sized fixation members toanchor to the blood vessels because scar tissue is not available.However, in one or more examples described in this disclosure, there maybe scarring of the tissue of tongue 40 allowing for smaller sizedfixation members 100A-100F (e.g., such that distance 104 from peak 102to lead 90 is approximately 2 mm).

In the example of FIGS. 6A-6D, there may be only two electrodes 98A and98B, rather than four electrodes 30, like FIG. 2. Having fewerelectrodes at distal end 94 allows for fixation members, like fixationmembers 100A-100F, to be closer to distal end 94, thereby increasing thenumber of fixation members 100A-100F that are deployed within tongue 40.For instance, if fixation members 100A-100F were more proximate todistal end 94, then there is a possibility that none of fixation members100A-100F will be implanted within tissue of tongue 40. For example, byhaving less than four electrodes, it may be possible that a distance 106from distal end 94 of lead 90 and the most proximal fixation member(e.g., fixation members 100C and 100F) is less than or equal to 10 mm.

In some examples, the diameter of lead 90 is less than 1.5 mm. Forexample, the diameter of lead 90 may be approximately 3.8 Fr (French),which is approximately 1.27 mm. Diameter sizes greater than 1.5 mm maybe possible. However, having the diameter of lead 90 less than 1.5 mmmay be desirable. For example, because lead 90 is to be implanted withinmusculature of tongue 40, there should be sufficient tissue surroundinglead 90 to ensure that lead 90 stays in place, especially after fixationmembers 100A-100F are deployed. Some other lead types, such as thoseused intravenously, may require wider diameter, such as 5 Fr, which isapproximately 1.67 mm, to ensure that when its fixation members aredeployed, that the lead stays within the blood vessels. With theanatomical structure of tongue 40 being different than veins and withlead 90 being implanted in musculature, instead of vasculature, havingwider diameter leads may not be needed, and in some cases may negativelyimpact the functionality of the lead. For instance, as described above,due to movement of tongue 40, especially as compared to movement ofvasculature, there may be benefits with ensuring high flexibility oflead 90. By having a thinner diameter (e.g., 3.8 Fr instead of 5 Fr),there may be an increase in flexibility of lead 90.

In some cases, fixation members 100A-100F may be permanently deployed.However, there may be cases where fixation members 100A-100F need not bepermanently deployed. For instance, once lead 90 is deployed, lead 90may be re-positioned after surgery or after trialing period. To addressthis, in some examples, tines may be used (e.g., in addition to bow-likefixation members). The tines may be deployed but the bow-like fixationmembers may not be deployed until determining that no further leadrepositioning is needed.

However, it may be possible to deploy the bow-like fixation members suchas where the bow-like fixation members are retractable (e.g., using apulling tubing that pulls the fixation members back to the body of lead90). For example, FIGS. 6A-6D illustrate opening 108 in collar 101D. Insome examples, to retract fixation members 100A-100F, a hook of apulling device is inserted in to opening 108 and the pulling device ispulled back proximally to retract fixation members 100A-100F.

In the above examples, collar 101A is described as being fixed andcollar 101D is described as having opening 108. However, the exampletechniques are not so limited. In some examples, collar 101A may includeopening 108 and collar 101D may be fixed. In such examples, a pushingmember may be inserted from distal end 94 to apply the compressionpressure or a hook of the pushing device may be put into opening 108 andused to push collar 101A proximally to apply the compression pressure. Apulling device, which may be same as pushing device, may be used to hookinto opening 108, in examples where opening 108 is on collar 101A, andpulled distally to retract fixation members 100A-100F.

To allow repositioning, in some examples, the tines may not beone-directional. That is, a tine can rotate 180° from a joint at lead90. For example, a tine may be initially pointed towards proximal end 96and can be rotated such that the tine can point towards distal end 94.In some examples, the tines can be perpendicular to lead 90 by extendingdirectly radially without being angled in an orientation opposite ofentry. In this way, there may not be a “fish hook” effect, allowing lead90 to be moved proximal or distal without the tines digging into tissue.

There could additionally or alternatively be a mechanical fixation ofthe tine or the tines may be in the form of a “screw thread” enablinginsertion and retraction by twisting lead 90. Another type of removablefixation member may have the tines curved around the circumference ofthe electrode shaft. Turning in one direction would deploy, and in otherdirection retract the tines. The benefit may be less tissue traumaduring removal, re-positioning, or replacement of the lead after scaringof the tissue.

In some examples, once fixation members 100A-100F (e.g., bow-likefixation members being arc shape, triangular shaped, or lobe shaped,and/or tines) are deployed, extraction of lead 90 may be problematic,whether part of intra-operative or post-surgery. To ease extraction, insome examples, fixation members 100A-100F may be retractable or made todissolve to avoid trauma to the patient during any movement of lead 90.Accordingly, in some examples, one or more of the one or more fixationmembers 100A-100F are configured to be retractable. Additionally oralternatively, one or more of the one or more fixation members 100A-100Fmay be configured to dissolve after deployment. Examples of fixationmembers 100A-100F that dissolve include aresynthetic polymer materials,such as polydioxanone, polyglycolic acid, polyglyconate, and polylacticacid (e.g., PL Poly(L-Iactide), PC Poly(ε-caprolactone), PLCPoly(L-Iactide/ε-caprolactone), PLG Poly(L-Iactide/Glycolide), PDLPoly(DL-Iactide), PLDL Poly(L-DL Iactide), and PG Poly(Glycolide). Asdescribed above, scarring of tissue of tongue 40 may fix lead 90 inplace. Accordingly, even if fixation members 100A-100F are retracted ordissolved, the chances of lead 90 migrating may be minimal.

FIGS. 7A-7C are conceptual diagrams illustrating examples of deployedbow-like members. FIG. 7A illustrates lead 110A, which is similar toleads 20 and 90. Lead 110A includes collars 114A and 115A and bow-likemember 112A. Initially, collars 114A and 115A may be further apart fromone another, and bow-like member 112A may rest along the elongatedmember of lead 110A. In response to a compression force (e.g., pushingor pulling), collars 114A and 115A come closer together and bow-likemember 112A bows out to form a lobe shape illustrated in FIG. 7A.

As illustrated, bow-like member 112A connects to collar 114A at firstconnection point 122A and to collar 115A at second connection point124A. Bow-like member 112A may be epoxied, formed as part of, crimped,welded, soldered, or the like to first connection point 122A and secondconnection point 124A.

When deployed, bow-like member 112A defines peak 120A. Peak 120A may bepoint of bow-like member 112A that is furthest from the elongated memberof lead 110A. In some examples, tangent line 116A at the point of peak120A is parallel with the longitudinal axis of lead 110A (e.g., parallelwith lead 110A). Also, line 118A extending from peak 120A to theelongated member of lead 110A may be substantially perpendicular to thelongitudinal axis (e.g., substantially perpendicular to elongated memberof lead 110A). In some examples, line 118A may intersect the elongatedmember of lead 110A substantially midway (e.g., halfway) between firstconnection point 122A and second connection point 124B. That is, line118A that intersects lead 110A and peak 120A crosses the midway pointbetween first connection point 122A and second connection point 124A. Asillustrated, there is only one peak 120A between first connection point122A and second connection point 124A. In some examples, the length ofline 118A is approximately 2 mm. In some examples, the ratio of thelength of line 118A to the diameter of lead 110A may be approximately1.5 (e.g., 1.3 to 1.8) or approximately 2 (e.g., 1.8 to 2.2).

FIG. 7B illustrates lead 110B, which is similar to leads 20 and 90. Lead110B includes collars 114B and 115B and bow-like member 112B. Initially,collars 114B and 115B may be further apart from one another, andbow-like member 112B may rest along the elongated member of lead 110B.In response to a compression force (e.g., pushing or pulling), collars114B and 115B come closer together and bow-like member 112B bows out toform an arc shape illustrated in FIG. 7B.

As illustrated, bow-like member 112B connects to collar 114B at firstconnection point 122B and to collar 115B at second connection point124B. Bow-like member 112B may be epoxied, formed as part of, crimped,welded, soldered, or the like to first connection point 122B and secondconnection point 124B.

When deployed, bow-like member 112B defines peak 120B. Peak 120B may bepoint of bow-like member 112B that is furthest from the elongated memberof lead 110B. In some examples, tangent line 116B at the point of peak120B is parallel with the longitudinal axis of lead 110B (e.g., parallelwith lead 110B). Also, line 118B extending from peak 120B to theelongated member of lead 110B may be substantially perpendicular to thelongitudinal axis (e.g., substantially perpendicular to elongated memberof lead 110B). In some examples, line 118B may intersect the elongatedmember of lead 110B substantially midway (e.g., halfway) between firstconnection point 122B and second connection point 124B. That is, line118B that intersects lead 110B and peak 120B crosses the midway pointbetween first connection point 122B and second connection point 124B. Asillustrated, there is only one peak 120B between first connection point122B and second connection point 124B. In some examples, the length ofline 118B is approximately 2 mm. In some examples, the ratio of thelength of line 118B to the diameter of lead 110B may be approximately1.5 (e.g., 1.3 to 1.8) or approximately 2 (e.g., 1.8 to 2.2).

FIG. 7C illustrates lead 110C, which is similar to leads 20 and 90. Lead110C includes collars 114C and 115C and bow-like member 112C. Initially,collars 114C and 115C may be further apart from one another, andbow-like member 112C may rest along the elongated member of lead 110C.In response to a compression force (e.g., pushing or pulling), collars114C and 115C come closer together and bow-like member 112C bows out toform a triangular shape illustrated in FIG. 7C.

As illustrated, bow-like member 112C connects to collar 114C at firstconnection point 122C and to collar 115C at second connection point124C. Bow-like member 112C may be epoxied, formed as part of, crimped,welded, soldered, or the like to first connection point 122C and secondconnection point 124C. To form a triangular shape, there may be a jointat the midway point between first connection point 122C and secondconnection point 124C that defines two segments of bow-like member 112C.For instance, a first segment is from first connection point 122C to thejoint and a second segment is from second connection point 124C to thejoint. As the compression force is applied, the joint moves outward todefine peak 120C.

When deployed, bow-like member 112C defines peak 120C. Peak 120C may bepoint of bow-like member 112C that is furthest from the elongated memberof lead 110C. In some examples, tangent line 116C at the point of peak120C is parallel with the longitudinal axis of lead 110C (e.g., parallelwith lead 110C). Also, line 118C extending from peak 120C to theelongated member of lead 110C may be substantially perpendicular to thelongitudinal axis (e.g., substantially perpendicular to elongated memberof lead 110C). In some examples, line 118C may intersect the elongatedmember of lead 110C substantially midway (e.g., halfway) between firstconnection point 122C and second connection point 124C. That is, line118C that intersects lead 110C and peak 120C crosses the midway pointbetween first connection point 122C and second connection point 124C. Asillustrated, there is only one peak 120C between first connection point122C and second connection point 124C. In some examples, the length ofline 118C is approximately 2 mm. In some examples, the ratio of thelength of line 118C to the diameter of lead 110C may be approximately1.5 (e.g., 1.3 to 1.8) or approximately 2 (e.g., 1.8 to 2.2).

FIG. 8 is a top perspective of a lead with deployed fixation members. Asdescribed above, in some examples, there may be a plurality of fixationmembers located at different circumferential positions around elongatedmember 93 of lead 90. FIG. 8 illustrates an example of plurality offixation members that extend radially outward from elongated member 93and located around elongated member 93 at different circumferentialpositions. For instance, similar to FIGS. 6A-6D, FIG. 8 illustratesfixation members 100A and 100D. In addition, FIG. 8 illustrates fixationmembers 100G and 100H. Fixation members 100G and 100H may be similar tofixation members 100A and 100D and may located at the same axial levelas fixation members 100A and 100D, but at different circumferentialpositions about the outer surface of the lead body, e.g., separated fromone another in the example of FIG. 8 by approximately 90°. Although fourfixation members are illustrated in FIG. 8, in some examples, there maybe fewer (e.g., three, two, or one) or greater (e.g., more than four)fixation members. The width of each of fixation members 100A, 100D,100G, and 100H, as well as 100B, 100C, 100E, and 100F may be less than 2mm, and possibly within a range of 0.5 mm to 1.5 mm but widths greaterthan 2 mm are possible as well. In some examples, the width of each offixation members 100A-100H may be approximately one-tenth, one-fifth, orone-third the diameter of lead 90.

FIGS. 9A-9C are conceptual diagrams illustrating lead position afterimplantation. When tongue 40 is extended and retracted, there may bestress causing breakage of leads 20, 90, or 110A-100C or discomfort topatient 14. In some examples, leads 20, 90, or 110A-110C may beimplanted in a way to allow stress relief, as well as avoid kinking. Forexamples, FIGS. 9A-9C illustrate examples of lead positions 130A-130C,respectively. In FIGS. 9A-9C, the leads are orientated along theproximal to distal axis of tongue 40 (e.g., y-axis) and along thelateral axis of tongue 40 (e.g., x-axis).

FIGS. 9A-9C illustrate examples to ease with understanding and shouldnot be considered limiting. For instance, for leads 20, 90, or110A-110C, there are two portions: a first portion that is in tissue oftongue 40 and a second portion that is tunneled subcutaneously to IMD16. There may be relatively small curvature in the first portion. Forinstance, the amplitude of the curvature, shown by amplitude 132A and132B, may be approximately 5 to 6 mm. In the second portion, theamplitude of the curvature may be greater, such as 10 to 20 mm.

Also the numbers of curves shown in FIGS. 9A and 9B (e.g., where a curveis peak or a bend in the lead) may be approximately 1 to 3 curves(although more are possible as shown in FIGS. 9A and 9B), which arespread out over 2 to 3 cm, within the first portion (e.g., part of thein tongue 40). The number of curves in the second portion of the lead(e.g., tunneled to IMD 16 through neck) may be 2 to 6 curves spread outover 10 to 20 cm.

FIG. 9A illustrates an example of lead position 130A as a helix orcompound helix. In the example of FIG. 9A, lead position 130A may have aproperty that a tangent line at any point makes a substantial constantangle with an axis. For instance, lead position 130A may be similar to acoil spring or spiral staircase. A helix may be considered as a singlecoil, and a compound helix may be considered as taking a single coil andwrapping it into a larger coil. For example, a compound helix is lead20, 90, or 110A-110C curved to form a plurality of helixes, and theplurality of helixes are curved to form a compound helix (e.g., acompound helix is a plurality of helixes curved to form a helix). Theresulting structure is very flexible in the axial direction. If lead 20,90, or 110A-110C is made from this construction, the helix or compoundhelix structure reduces the axial load on lead 20, 90, or 110A-110C,reducing the likelihood of breakage or dislodgement

FIG. 9B illustrates an example of lead position 130B as a wave shape. Inthe example of FIG. 9B, lead position 130B may have a property that thelead forms a sinusoidal or sinusoidal-like shape once implanted. In someexamples, rather than a sinusoidal shape, the lead may be implanted in asaw-tooth shape.

FIG. 9C illustrates an example of lead position 130C where a loop isincluded in the lead after implantation. The location of the loop maygenerally be at any location along the lead body. The size of the loopmay be based on factors such as size of lead and discomfort to patient14.

Although FIGS. 9A-9C are illustrated separately, one or more of theexamples of FIGS. 9A-9C may be used together. For example, a loop may beincluded in the sinusoidal shape of the lead.

In general, shapes for stress relief of the lead include a helix, acompound helix, a wave or saw-tooth shape or even putting a loop intothe lead when relaxed. Electrodes 30 or 98A, 98B may be placed distal ormore proximal depending on the amount of relief desired. Extension oftongue 40 can move the electrodes away from or toward the hypoglossalnerve and/or motor points 54A, 54B, 55A, and/or 55B depending on thelocation of the stress relief pattern or position of lead. Moreover,variations in placement of the saw-tooth stress relief or the electrodescan enable the lead to maintain functioning after some amount ofdisplacement or movement.

FIG. 10 is a flowchart illustrating an example of lead implantation. Amedical professional may insert a needle through tissue near a chin ofpatient 14 and through tongue 40 of patient 14 (140). By inserting theneedle, the medical professional creates an opening for placement of alead like lead 20, 90, or 110A-110C. The medical professional may insertan introducer through an opening created by the needle (142).

The medical professional may insert a lead (e.g., lead 20, 90, or110A-110C) through the introducer to have a shape of one of a helix, acompound helix, a wave shape, or saw-tooth shape, or having a loop inthe lead implanted in tongue 40 (144). As described above, lead 20, 90,or 110A-110C may include an elongated member and one or more electrodesat a distal end of the elongated member such that the one or moreelectrodes are implanted proximate to one or more motor points (e.g.,motor points 54A, 54B, 55A, and/or 55B) of a protrusor muscle (e.g., atleast one of the genioglossal or geniohyoid muscle) within tongue 40 ofpatient 14.

The medical professional may deploy at least one fixation member of theone or more fixation members (e.g., 32, 100A-100F, or 112A-112C) (146).The at least one fixation member may be a bow-like member that, whendeployed, defines a peak (e.g., peak 33, 102, or 120A-120C) between afirst connection point on a first collar (e.g., collar 101A-101D, 114A,114B, 115A, 115B, 115C, or 115C) and a second connection point on asecond collar (e.g., collar 101A-101D, 114A, 114B, 115A, 115B, 115C, or115C) of the bow-like member. In some examples, the medical professionalmay deploy the at least one fixation member based on movement of theintroducer. For example, the introducer may hold fixation members100A-100F along the body of lead 90 and proximal movement of theintroducer may cause fixation members 100A-100F to deploy (e.g., due tospring bias). As another example, the medical professional may pull backthe introducer proximally to be more proximal than fixation members100A-100F, and then push the introducer distally to apply compressionpressure to distal collar 101D and cause fixation members 100A-100F todistend perpendicularly.

It should be noted that system 10, and the techniques described herein,may not be limited to treatment or monitoring of a human patient. Inalternative examples, system 10 may be implemented in non-humanpatients, e.g., primates, canines, equines, pigs, and felines. Theseother animals may undergo clinical or research therapies that my benefitfrom the subject matter of this disclosure. Various examples aredescribed herein, such as the following examples.

Example 1: A lead for delivering electrical stimulation therapy, thelead comprising an elongated member defining a longitudinal axis andcomprising a proximal end and a distal end, one or more electrodesdisposed at the distal end of the elongated member, a plurality ofcollars located along the longitudinal axis of the elongated member, andone or more fixation members, wherein at least one of the fixationmembers is a bow-like member having a first connection point to a firstcollar of the plurality of collars and a second connection point to asecond collar of the plurality of collars, wherein the distal end of theelongated member is configured for insertion in a tongue of a patientsuch that the one or more electrodes are implanted proximate to one ormore motor points of a protrusor muscle within the tongue of the patientand the bow-like member of the one or more fixation members is implantedwithin tissue of the tongue, and wherein the bow-like member, whendeployed, defines a peak between the first connection point and thesecond connection point of the bow-like member, and wherein the peak isa point of the bow-like member that is furthest from the elongatedmember.

Example 2. The lead of example 1, wherein a tangent line at the point ofthe peak is parallel with the longitudinal axis, and wherein a lineextending from the peak to the elongated member is substantiallyperpendicular to the longitudinal axis and intersects the elongatedmember substantially midway between the first connection point and thesecond connection point.

Example 3. The lead of any of examples 1 and 2, wherein the one or morefixation members, when deployed, comprise a triangular shape or a lobeshape.

Example 4. The lead of any of examples 1-3, wherein a distance betweenthe elongated member and the peak of the bow-like member isapproximately 2 millimeter (mm).

Example 5. The lead of any of examples 1-4, wherein a diameter of thelead is less than 1.5 mm.

Example 6. The lead of any of examples 1-5, wherein a distance betweenthe distal end of the lead and the bow-like member is less than or equalto 10 mm.

Example 7. The lead of any of examples 1-6, wherein the one or moreelectrodes comprise less than four electrodes.

Example 8. The lead of any of examples 1-7, wherein the bow-like memberis configured to deploy in response to movement of an introducer usedfor lead implantation.

Example 9. The lead of example 8, wherein the bow-like member isconfigured to deploy in response to the introducer pushing on a distalcollar of the plurality of collars.

Example 10. The lead of any of examples 1-9, wherein one or more of theone or more fixation members are configured to be retractable.

Example 11. The lead of any of examples 1-10, wherein one or more of theone or more fixation members are configured to dissolve afterdeployment.

Example 12. The lead of any of examples 1-11, wherein the lead isconfigured to have flexibility to form a shape of a helix, a compoundhelix, a wave shape, a saw-tooth shape, or include a loop in the leadafter implantation.

Example 13. A system for delivering electrical stimulation therapy, thesystem comprising a lead for delivering electrical stimulation therapy,the lead comprising an elongated member defining a longitudinal axis andcomprising a proximal end and a distal end, one or more electrodesdisposed at the distal end of the elongated member, a plurality ofcollars located along the longitudinal axis of the elongated member, andone or more fixation members, wherein at least one of the fixationmember is a bow-like member having a first connection point to a firstcollar of the plurality of collars and a second connection point to asecond collar of the plurality of collars, wherein the distal end of theelongated member is configured for insertion in a tongue of a patientsuch that the one or more electrodes are implanted proximate to one ormore motor points of least one of a genioglossal or geniohyoid musclewithin the tongue of the patient and the bow-like member of the one ormore fixation members is implanted within tissue of the tongue, andwherein the bow-like member, when deployed, defines a peak between thefirst connection point and the second connection point of the bow-likemember, and wherein the peak is a point of the bow-like member that isfurthest from the elongated member, and a medical device comprising aconnector assembly configured to couple to the proximal end of theelongated member of the lead, wherein the medical device is configuredto deliver electrical stimulation therapy via the one or more electrodesthat cause at least one of the genioglossal or geniohyoid muscle toprotrude the tongue of the patient.

Example 14. The system of example 13, wherein the lead comprises a firstlead comprising a first elongated member defining a first longitudinalaxis and comprising a first proximal end and a first distal end, a firstset of one or more electrodes, a first plurality of collars, and a firstset of one or more fixation members, wherein the bow-like membercomprises a first bow-like member, wherein the protrusor muscle is afirst protrusor muscle, and wherein the one or more motor pointscomprises a first set of motor points, the system further comprising asecond lead comprising a second elongated member defining a secondlongitudinal axis and comprising a second proximal end and a seconddistal end, a second set of one or more electrodes disposed at thedistal end of the second elongated member, a second plurality of collarslocated along the second longitudinal axis of the elongated member, anda second set of one or more fixation members, wherein at least one ofthe second set of fixation members is a second bow-like member having afirst connection point to a first collar of the second plurality ofcollars and a second connection point to a second collar of the secondplurality of collars, wherein the second distal end of the secondelongated member is implanted in the tongue of the patient such that thesecond set of one or more electrodes are implanted proximate to a secondset of motor points of a second protrusor muscle within the tongue ofthe patient and the second bow-like member is implanted within tissue ofthe tongue, and wherein the second bow-like member, when deployed,defines a peak between the first connection point to the first collar ofthe second plurality of collars and the second connection point to thesecond collar of the second plurality of collars of the second bow-likemember, and wherein the second peak is a point of the second bow-likemember that is furthest from the second elongated member.

Example 15. The system of any of examples 13 and 14, wherein at leastone of a distance between the lead and the peak of the at least onefixation member is approximately 2 millimeter (mm), a diameter of thelead is less than 1.5 mm, and a distance between the distal end of thelead and the at least one fixation member is less than or equal to 10mm.

Example 16. The system of any of examples 13-15, wherein the one or moreelectrodes comprise less than four electrodes.

Example 17. The system of any of examples 13-16, wherein the one or morefixation member, when deployed, comprise a triangular shape or a lobeshape.

Example 18. The system of any of examples 13-17, wherein one or more ofthe one or more fixation members are configured to, at least one of, beretractable or dissolve after deployment.

Example 19. A lead for delivering electrical stimulation therapy, thelead comprising an elongated member defining a longitudinal axis andcomprising a proximal end and a distal end, wherein the elongated memberhas a diameter less than 1.5 millimeter (mm), one or more electrodesdisposed at the distal end of the elongated member, a plurality ofcollars located along the longitudinal axis of the elongated member, andone or more fixation members, wherein at least one of the fixationmembers is a bow-like member having a first connection point to a firstcollar of the plurality of collars and a second connection point to asecond collar of the plurality of collars, and wherein the one or morefixation members, when deployed, comprise a triangular shape or a lobeshape, wherein the distal end of the elongated member is configured forinsertion in a tongue of a patient such that the one or more electrodesare implanted proximate to one or more motor points of a protrusormuscle within the tongue of the patient and the bow-like member of theone or more fixation members is implanted within tissue of the tongue,and wherein the bow-like member, when deployed, defines a peak betweenthe first connection point and the second connection point of thebow-like member, and wherein the peak is a point of the bow-like memberthat is furthest from the elongated member, wherein a distance betweenthe lead and the peak of the bow-like member is approximately 2millimeter, and wherein a distance between the distal end of theelongated member and the bow-like member is less than or equal to 10 mm.

Example 20. The lead of example 19, wherein the one or more electrodescomprise less than four electrodes.

Example 21. The lead of any of examples 19 and 20, wherein the bow-likemember is configured to deploy in response to movement of an introducerused for lead implantation.

Example 22. The lead of any of examples 19-21, wherein one or more ofthe one or more fixation members are at least one of configured to beretractable or configured to dissolve after deployment.

Example 23. The lead of any of examples 19-22, wherein the lead isconfigured to have flexibility to form a shape of a helix, a compoundhelix, a wave shape, a saw-tooth shape, or include a loop in the leadafter implantation.

Example 24. A method of implanting a lead, the method comprisinginserting a needle through tissue near a chin of a patient and through atongue of the patient, inserting an introducer through an openingcreated by the needle, and inserting a lead through the introducer, thelead comprising an elongated member and one or more electrodes at adistal end of the elongated member such that the one or more electrodesare implanted proximate to one or more motor points of a protrusormuscle within the tongue of the patient, wherein inserting the leadcomprises inserting the lead to have a shape of one of a helix, acompound helix, a wave shape, or saw-tooth shape, or having a loop inthe lead.

Example 25. The method of example 24, deploying at least one fixationmember of the one or more fixation members, wherein the at least onefixation member, when deployed, defines a peak between a firstconnection point on a first collar on the lead and a second connectionpoint on a second collar on the lead, and wherein the peak is a point ofthe at least one fixation member that is furthest from the elongatedmember.

Example 26. The method of example 25, wherein deploying the at least onefixation member comprises deploying the at least one fixation memberbased on movement of the introducer.

The techniques of this disclosure may be implemented in a wide varietyof computing devices, medical devices, or any combination thereof. Anyof the described units, modules or components may be implementedtogether or separately as discrete but interoperable logic devices.Depiction of different features as modules or units is intended tohighlight different functional aspects and does not necessarily implythat such modules or units must be realized by separate hardware orsoftware components. Rather, functionality associated with one or moremodules or units may be performed by separate hardware or softwarecomponents, or integrated within common or separate hardware or softwarecomponents.

The disclosure contemplates computer-readable storage media comprisinginstructions to cause a processor to perform any of the functions andtechniques described herein. The computer-readable storage media maytake the example form of any volatile, non-volatile, magnetic, optical,or electrical media, such as a RAM, ROM, NVRAM, EEPROM, or flash memorythat is tangible. The computer-readable storage media may be referred toas non-transitory. A server, client computing device, or any othercomputing device may also contain a more portable removable memory typeto enable easy data transfer or offline data analysis.

The techniques described in this disclosure, including those attributedto various modules and various constituent components, may beimplemented, at least in part, in hardware, software, firmware or anycombination thereof. For example, various aspects of the techniques maybe implemented within one or more processors, including one or moremicroprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated,discrete logic circuitry, or other processing circuitry, as well as anycombinations of such components, remote servers, remote client devices,or other devices. The term “processor” or “processing circuitry” maygenerally refer to any of the foregoing logic circuitry, alone or incombination with other logic circuitry, or any other equivalentcircuitry.

Such hardware, software, firmware may be implemented within the samedevice or within separate devices to support the various operations andfunctions described in this disclosure. In addition, any of thedescribed units, modules or components may be implemented together orseparately as discrete but interoperable logic devices. Depiction ofdifferent features as modules or units is intended to highlightdifferent functional aspects and does not necessarily imply that suchmodules or units must be realized by separate hardware or softwarecomponents. Rather, functionality associated with one or more modules orunits may be performed by separate hardware or software components, orintegrated within common or separate hardware or software components.For example, any module described herein may include electricalcircuitry configured to perform the features attributed to thatparticular module, such as fixed function processing circuitry,programmable processing circuitry, or combinations thereof.

The techniques described in this disclosure may also be embodied orencoded in an article of manufacture including a computer-readablestorage medium encoded with instructions. Instructions embedded orencoded in an article of manufacture including a computer-readablestorage medium encoded, may cause one or more programmable processors,or other processors, to implement one or more of the techniquesdescribed herein, such as when instructions included or encoded in thecomputer-readable storage medium are executed by the one or moreprocessors. Example computer-readable storage media may include randomaccess memory (RAM), read only memory (ROM), programmable read onlymemory (PROM), erasable programmable read only memory (EPROM),electronically erasable programmable read only memory (EEPROM), flashmemory, a hard disk, a compact disc ROM (CD-ROM), a floppy disk, acassette, magnetic media, optical media, or any other computer readablestorage devices or tangible computer readable media. Thecomputer-readable storage medium may also be referred to as storagedevices.

In some examples, a computer-readable storage medium comprisesnon-transitory medium. The term “non-transitory” may indicate that thestorage medium is not embodied in a carrier wave or a propagated signal.In certain examples, a non-transitory storage medium may store data thatcan, over time, change (e.g., in RAM or cache).

Various examples have been described herein. Any combination of thedescribed operations or functions is contemplated. These and otherexamples are within the scope of the following claims.

What is claimed is:
 1. A lead for delivering electrical stimulationtherapy, the lead comprising: an elongated member defining alongitudinal axis and comprising a proximal end and a distal end; one ormore electrodes disposed at the distal end of the elongated member; aplurality of collars located along the longitudinal axis of theelongated member; and one or more fixation members, wherein at least oneof the fixation members is a bow-like member having a first connectionpoint to a first collar of the plurality of collars and a secondconnection point to a second collar of the plurality of collars, whereinthe first collar and the second collar are configured to be slidablealong the longitudinal axis of the elongated member, wherein the distalend of the elongated member is configured for insertion in a tongue of apatient such that the one or more electrodes are configured to beimplanted proximate to one or more motor points of a protrusor musclewithin the tongue of the patient and the bow-like member of the one ormore fixation members is configured to be implanted within tissue of thetongue, wherein the bow-like member, when deployed, defines only onepeak between the first connection point and the second connection pointof the bow-like member, wherein the peak is a point of the bow-likemember that is furthest from the elongated member, and wherein the firstcollar and the second collar sliding along the longitudinal axis of theelongated member are configured to cause the bow-like member to deployfrom an undeployed state in which the bow-like member rests flat alongthe elongated member to a deployed state in which the bow-like memberexhibits the peak.
 2. The lead of claim 1, wherein a tangent line at thepoint of the peak is parallel with the longitudinal axis, and wherein aline extending from the peak to the elongated member is substantiallyperpendicular to the longitudinal axis and intersects the elongatedmember substantially midway between the first connection point and thesecond connection point.
 3. The lead of claim 1, wherein the one or morefixation members, when deployed, comprise a triangular shape or a lobeshape.
 4. The lead of claim 1, wherein a distance between the elongatedmember and the peak of the bow-like member is approximately 2 millimeter(mm).
 5. The lead of claim 1, wherein a diameter of the lead is lessthan 1.5 mm.
 6. The lead of claim 1, wherein a distance between thedistal end of the lead and the bow-like member is less than or equal to10 mm.
 7. The lead of claim 1, wherein the one or more electrodescomprise less than four electrodes.
 8. The lead of claim 1, wherein thebow-like member is configured to deploy in response to movement of anintroducer used for lead implantation.
 9. The lead of claim 8, whereinthe bow-like member is configured to deploy in response to theintroducer pushing on a distal collar of the plurality of collars. 10.The lead of claim 1, wherein one or more of the one or more fixationmembers are configured to be retractable.
 11. The lead of claim 1,wherein one or more of the one or more fixation members are configuredto dissolve after deployment.
 12. The lead of claim 1, wherein the leadis configured to have flexibility to form a shape of a helix, a compoundhelix, a wave shape, a saw-tooth shape, or include a loop in the leadafter implantation.
 13. A system for delivering electrical stimulationtherapy, the system comprising: a lead for delivering electricalstimulation therapy, the lead comprising: an elongated member defining alongitudinal axis and comprising a proximal end and a distal end; one ormore electrodes disposed at the distal end of the elongated member; aplurality of collars located along the longitudinal axis of theelongated member; and one or more fixation members, wherein at least oneof the fixation member is a bow-like member having a first connectionpoint to a first collar of the plurality of collars and a secondconnection point to a second collar of the plurality of collars, whereinthe first collar and the second collar are configured to be slidablealong the longitudinal axis of the elongated member, wherein the distalend of the elongated member is configured for insertion in a tongue of apatient such that the one or more electrodes are configured to beimplanted proximate to one or more motor points of least one of agenioglossal or geniohyoid muscle within the tongue of the patient andthe bow-like member of the one or more fixation members is configured tobe implanted within tissue of the tongue, wherein the bow-like member,when deployed, defines only one peak between the first connection pointand the second connection point of the bow-like member, wherein the peakis a point of the bow-like member that is furthest from the elongatedmember, and wherein the first collar and the second collar sliding alongthe longitudinal axis of the elongated member are configured to causethe bow-like member to deploy from an undeployed state in which thebow-like member rests flat along the elongated member to a deployedstate in which the bow-like member exhibits the peak; and a medicaldevice comprising a connector assembly configured to couple to theproximal end of the elongated member of the lead, wherein the medicaldevice is configured to deliver electrical stimulation therapy via theone or more electrodes that cause at least one of the genioglossal orgeniohyoid muscle to protrude the tongue of the patient.
 14. The systemof claim 13, wherein the lead is a first lead comprising a firstelongated member defining a first longitudinal axis and comprising afirst proximal end and a first distal end, a first set of one or moreelectrodes, a first plurality of collars, and a first set of one or morefixation members, wherein the bow-like member comprises a first bow-likemember, and wherein the one or more motor points comprises a first setof motor points, the system further comprising a second lead comprising:a second elongated member defining a second longitudinal axis andcomprising a second proximal end and a second distal end; a second setof one or more electrodes disposed at the distal end of the secondelongated member; a second plurality of collars located along the secondlongitudinal axis of the elongated member; and a second set of one ormore fixation members, wherein at least one of the second set offixation members is a second bow-like member having a first connectionpoint to a first collar of the second plurality of collars and a secondconnection point to a second collar of the second plurality of collars,wherein the second distal end of the second elongated member isconfigured to be implanted in the tongue of the patient such that thesecond set of one or more electrodes are configured to be implantedproximate to a second set of motor points within the tongue of thepatient and the second bow-like member is configured to be implantedwithin tissue of the tongue, and wherein the second bow-like member,when deployed, defines a peak between the first connection point to thefirst collar of the second plurality of collars and the secondconnection point to the second collar of the second plurality of collarsof the second bow-like member, and wherein the second peak is a point ofthe second bow-like member that is furthest from the second elongatedmember.
 15. The system of claim 13, wherein at least one of: a distancebetween the lead and the peak of the at least one fixation member isapproximately 2 millimeter (mm), a diameter of the lead is less than 1.5mm, and a distance between the distal end of the lead and the at leastone fixation member is less than or equal to 10 mm.
 16. The system ofclaim 13, wherein the one or more electrodes comprise less than fourelectrodes.
 17. The system of claim 13, wherein the one or more fixationmember, when deployed, comprise a triangular shape or a lobe shape. 18.The system of claim 13, wherein one or more of the one or more fixationmembers are configured to, at least one of, be retractable or dissolveafter deployment.
 19. A lead for delivering electrical stimulationtherapy, the lead comprising: an elongated member defining alongitudinal axis and comprising a proximal end and a distal end,wherein the elongated member has a diameter less than 1.5 millimeter(mm); one or more electrodes disposed at the distal end of the elongatedmember; a plurality of collars located along the longitudinal axis ofthe elongated member; and one or more fixation members, wherein at leastone of the fixation members is a bow-like member having a firstconnection point to a first collar of the plurality of collars and asecond connection point to a second collar of the plurality of collars,wherein the first collar and the second collar are configured to beslidable along the longitudinal axis of the elongated member, whereinthe distal end of the elongated member is configured for insertion in atongue of a patient such that the one or more electrodes are configuredto be implanted proximate to one or more motor points of a protrusormuscle within the tongue of the patient and the bow-like member of theone or more fixation members is configured to be implanted within tissueof the tongue, wherein the bow-like member, when deployed, defines onlyone peak between the first connection point and the second connectionpoint of the bow-like member, wherein the peak is a point of thebow-like member that is furthest from the elongated member, and whereinthe first collar and the second collar sliding along the longitudinalaxis of the elongated member are configured to cause the bow-like memberto deploy from an undeployed state in which the bow-like member restsflat along the elongated member to a deployed state in which thebow-like member exhibits the peak, wherein a distance between the leadand the peak of the bow-like member is approximately 2 millimeter, andwherein a distance between the distal end of the elongated member andthe bow-like member is less than or equal to 10 mm.
 20. The lead ofclaim 19, wherein the one or more electrodes comprise less than fourelectrodes.
 21. The lead of claim 19, wherein the bow-like member isconfigured to deploy in response to movement of an introducer used forlead implantation.
 22. The lead of claim 19, wherein one or more of theone or more fixation members are at least one of configured to beretractable or configured to dissolve after deployment.
 23. The lead ofclaim 19, wherein the lead is configured to have flexibility to form ashape of a helix, a compound helix, a wave shape, a saw-tooth shape, orinclude a loop in the lead after implantation.